# uChecker

> Сервис проверки и валидации email-адресов: SMTP-проверка существования
> ящика, MX-записи, спам-ловушки, одноразовые и ролевые адреса, чистка базы
> рассылки. Плюс бесплатные инструменты для почтовой аутентификации —
> SPF, DKIM, DMARC, MTA-STS, BIMI, TLS-RPT — и справочные материалы по
> доставляемости на русском и английском языках.

Веб-приложение живёт на app.uchecker.net, HTTP API — на api.uchecker.net.
Полный перечень адресов: https://uchecker.net/sitemap.xml

## Основные страницы

- [Главная (RU)](https://uchecker.net/): Проверка email онлайн, тарифы, FAQ
- [Home (EN)](https://uchecker.net/en): Email verification and bulk list cleaning
- [Инструменты (RU)](https://uchecker.net/instrumenty): Хаб бесплатных инструментов
- [Tools (EN)](https://uchecker.net/tools): Free email infrastructure tools
- [Блог (RU)](https://uchecker.net/blog): Статьи о email-маркетинге и доставляемости
- [Blog (EN)](https://uchecker.net/blog-en): Email marketing and deliverability guides
- [Глоссарий (RU)](https://uchecker.net/glossary): Термины валидации и доставляемости
- [Glossary (EN)](https://uchecker.net/glossary-en): Validation and deliverability terms
- [MCP-сервер (RU)](https://uchecker.net/mcp): Валидация email для AI-агентов
- [MCP server (EN)](https://uchecker.net/en/mcp): Email validation for AI agents

## Инструменты (RU)

- [Проверка почтового домена](https://uchecker.net/proverka-pochtovogo-domena): Все семь проверок разом и оценка настройки от 0 до 100. С этого стоит начинать.
- [Проверка SPF](https://uchecker.net/proverka-spf-zapisi): Синтаксис записи, раскрытая цепочка include и счётчик десяти разрешённых DNS-запросов.
- [Проверка DKIM](https://uchecker.net/proverka-dkim): Ключ по селектору или перебор двух десятков известных. Тип ключа, длина, отзыв.
- [Проверка DMARC](https://uchecker.net/proverka-dmarc): Разбор политики по тегам и проверка того, что внешние адреса отчётов авторизованы.
- [Проверка MX](https://uchecker.net/proverka-mx-zapisej): Почтовые серверы с приоритетами, их IP-адреса и определение провайдера.
- [Валидатор SPF](https://uchecker.net/validaciya-spf-zapisi): Проверка записи, вставленной текстом, — до публикации в DNS.
- [Генератор SPF](https://uchecker.net/generator-spf-zapisi): Сборка записи по списку сервисов с подсказками include и живым счётчиком DNS-запросов.
- [Генератор DMARC](https://uchecker.net/generator-dmarc-zapisi): Политика, поддомены, отчёты и выравнивание — с объяснением каждого тега.
- [Генератор ключа DKIM](https://uchecker.net/generator-dkim-klyucha): Пара ключей RSA прямо в браузере: закрытая часть не уходит на сервер.
- [Генератор BIMI](https://uchecker.net/generator-bimi-zapisi): Запись для показа логотипа рядом с письмом и требования к нему.
- [Генератор MTA-STS](https://uchecker.net/generator-mta-sts): TXT-запись и файл политики: защита соединения от понижения до открытого текста.
- [Генератор TLS-RPT](https://uchecker.net/generator-tls-rpt): Отчёты о неудачных попытках установить шифрованное соединение.

## Tools (EN)

- [Email domain health check](https://uchecker.net/email-domain-health-check): All seven checks at once with a setup score from 0 to 100. The place to start.
- [SPF checker](https://uchecker.net/spf-checker): Record syntax, the expanded include chain and a counter for the ten allowed DNS lookups.
- [DKIM checker](https://uchecker.net/dkim-checker): Key by selector, or a probe of two dozen known ones. Key type, length and revocation.
- [DMARC checker](https://uchecker.net/dmarc-checker): Tag-by-tag policy breakdown plus verification that external report addresses are authorised.
- [MX lookup](https://uchecker.net/mx-lookup): Mail servers with priorities, their IP addresses and mail provider detection.
- [SPF validator](https://uchecker.net/spf-record-validator): Validate a pasted record before it ever goes into DNS.
- [SPF generator](https://uchecker.net/spf-record-generator): Build a record from your services, with verified include values and a live DNS lookup counter.
- [DMARC generator](https://uchecker.net/dmarc-record-generator): Policy, subdomains, reporting and alignment — with every tag explained.
- [DKIM key generator](https://uchecker.net/dkim-record-generator): An RSA key pair created in your browser: the private half never leaves it.
- [BIMI generator](https://uchecker.net/bimi-record-generator): The record that puts your logo beside your mail, and what it demands.
- [MTA-STS generator](https://uchecker.net/mta-sts-generator): TXT record and policy file: protection against downgrading a connection to plaintext.
- [TLS-RPT generator](https://uchecker.net/tls-rpt-generator): Reports about failed attempts to establish an encrypted connection.

## Глоссарий (RU)

- [Спам-ловушки](https://uchecker.net/glossary/spam-lovushki-chto-takoe): Спам-ловушки - это email-адреса, созданные или переиспользованные для выявления спамеров. Разбираем типы, как попадают в базу и как избежать.
- [Catch-all email](https://uchecker.net/glossary/catch-all-email-chto-eto): Catch-all (accept-all) - настройка почтового сервера, при которой принимаются письма на любой адрес домена. Чем опасно и как проверять.
- [Ролевые адреса](https://uchecker.net/glossary/rolevye-adresa-email): Ролевые адреса (info@, support@, admin@) - это email, привязанные к функции, а не к человеку. Почему их опасно включать в рассылки.
- [Одноразовые почты](https://uchecker.net/glossary/odnorazovye-pochty-temp-mail): Временные email (disposable email) - адреса, которые живут от 10 минут до нескольких часов. Как их определить и зачем фильтровать.
- [Грейлистинг](https://uchecker.net/glossary/chto-takoe-greylisting): Грейлистинг - метод защиты от спама, при котором сервер временно отклоняет письмо от неизвестного отправителя. Как это влияет на валидацию.
- [SMTP-проверка](https://uchecker.net/glossary/chto-takoe-smtp-proverka): SMTP-проверка (SMTP verification) - метод валидации email через подключение к почтовому серверу без отправки письма. Как работает, ограничения.
- [Синтаксическая валидация email](https://uchecker.net/glossary/sintaksicheskaya-validaciya-email): Проверка формата email-адреса по правилам RFC 5321/5322: допустимые символы, структура, длина.
- [Проверка MX-записи](https://uchecker.net/glossary/proverka-mx-zapisi): Как работает проверка MX-записи домена при валидации email и что она даёт.
- [Проверка email в реальном времени](https://uchecker.net/glossary/proverka-email-v-realnom-vremeni): Real-time верификация email через API: как работает, зачем нужна, как интегрировать.
- [Пакетная проверка email](https://uchecker.net/glossary/paketaya-proverka-email): Массовая валидация email-списков: загрузка файла, обработка, результаты.
- [Double opt-in](https://uchecker.net/glossary/double-opt-in-glossary): Двойное подтверждение подписки: как работает, зачем нужно и когда обязательно.
- [Hard bounce](https://uchecker.net/glossary/hard-bounce-glossary): Жёсткий возврат письма: причины, SMTP-коды, как обрабатывать и предотвращать.
- [Soft bounce](https://uchecker.net/glossary/soft-bounce-glossary): Мягкий возврат письма: временные ошибки доставки и правила обработки.
- [Обнаружение опечаток в email](https://uchecker.net/glossary/typo-detection): Как системы валидации находят и исправляют опечатки в email-адресах.
- [Email append](https://uchecker.net/glossary/email-append): Обогащение данных: поиск email-адреса по имени и компании. Легальность и риски.
- [Проверка существования почтового ящика](https://uchecker.net/glossary/proverka-sushchestvovaniya-pochtovogo-yashchika): Как валидатор проверяет, существует ли конкретный почтовый ящик на сервере.
- [Гигиена email-базы](https://uchecker.net/glossary/gigiena-email-bazy-glossary): Процесс регулярной очистки и поддержания качества email-списка.
- [Дедупликация email](https://uchecker.net/glossary/deduplication-email): Удаление дубликатов email-адресов из базы: методы и инструменты.
- [API валидации email](https://uchecker.net/glossary/email-validation-api-glossary): Программный интерфейс для проверки email-адресов: endpoint, параметры, ответ.
- [Неактивные подписчики](https://uchecker.net/glossary/neaktivnye-podpischiki): Подписчики, которые перестали открывать и кликать. Как определить и что делать.
- [Сегментация email-списка](https://uchecker.net/glossary/segmentaciya-email-spiska): Разделение базы подписчиков на группы для таргетированных рассылок.
- [Отравленные данные](https://uchecker.net/glossary/poisoned-data): Фейковые и вредоносные email-адреса, намеренно внесённые в базу.
- [Email scoring](https://uchecker.net/glossary/email-scoring): Скоринг email-адресов: оценка риска и качества каждого адреса в базе.
- [Webhook валидации email](https://uchecker.net/glossary/webhook-validacii): Автоматическое уведомление о результатах проверки через callback URL.
- [Неопределённый статус email](https://uchecker.net/glossary/unknown-email-status): Когда валидатор не может точно определить, существует ли адрес. Причины и действия.
- [Бесплатные почтовые провайдеры](https://uchecker.net/glossary/free-email-provider): Gmail, Яндекс.Почта, Mail.ru и другие. Особенности валидации и рассылок.
- [Корпоративная почта](https://uchecker.net/glossary/korporativnaya-pochta): Email на собственном домене: особенности, валидация, B2B-значимость.
- [Honeypot-поля в формах](https://uchecker.net/glossary/honeypot-polya-form): Скрытые поля для защиты форм подписки от ботов.
- [Бот-регистрации](https://uchecker.net/glossary/bot-signups): Автоматические регистрации ботов через формы подписки. Защита и фильтрация.
- [Адреса жалобщиков](https://uchecker.net/glossary/complaint-address): Подписчики, которые жалуются на спам. Почему их нужно исключать из рассылок.
- [Suppression list](https://uchecker.net/glossary/suppression-list): Список подавления: адреса, на которые нельзя отправлять рассылки.
- [DNS-валидация email](https://uchecker.net/glossary/dns-validaciya-email): Проверка email через DNS-запросы: MX, A, TXT-записи домена.
- [Проверка доменного возраста](https://uchecker.net/glossary/proverka-domennogo-vozrasta): Как возраст домена помогает оценить риск email-адреса.
- [GDPR и email-маркетинг](https://uchecker.net/glossary/gdpr-i-email-glossary): Европейский регламент о персональных данных и его требования к email-рассылкам.
- [CAN-SPAM Act](https://uchecker.net/glossary/can-spam-act): Американский закон о коммерческих email-рассылках: требования и штрафы.
- [ФЗ О рекламе и email-рассылки](https://uchecker.net/glossary/federalnyj-zakon-o-reklame-email): Российский закон о рекламе: требования к email-рассылкам и штрафы.
- [Single opt-in](https://uchecker.net/glossary/single-opt-in-glossary): Подписка без подтверждения: плюсы, минусы и когда допустимо.
- [Confirmed opt-in](https://uchecker.net/glossary/confirmed-opt-in): Подтверждённая подписка: отличия от double opt-in и когда использовать.
- [Проверка email по чёрным спискам](https://uchecker.net/glossary/email-blacklist-check): Как проверить, находится ли домен или IP в DNSBL.
- [Accept-all домен](https://uchecker.net/glossary/accept-all-domen): Домен, который принимает почту на любой адрес. Чем опасно для рассылок.
- [Точность верификации email](https://uchecker.net/glossary/email-verification-accuracy): Как измеряется точность валидатора: false positive, false negative, precision, recall.
- [Репутация отправителя](https://uchecker.net/glossary/reputaciya-otpravitelya-glossary): Совокупная оценка надёжности отправителя email почтовыми провайдерами.
- [Sender Score](https://uchecker.net/glossary/sender-score): Числовой рейтинг репутации отправителя от 0 до 100 по версии Validity.
- [Доменная репутация](https://uchecker.net/glossary/domennaya-reputaciya): Репутация домена отправителя у почтовых провайдеров. Как формируется и проверяется.
- [IP-репутация](https://uchecker.net/glossary/ip-reputaciya): Репутация IP-адреса, с которого отправляются email. Dedicated vs shared.
- [Прогрев IP-адреса](https://uchecker.net/glossary/progrev-ip-adresa): Постепенное увеличение объёма отправки с нового IP для наращивания репутации.
- [Прогрев домена](https://uchecker.net/glossary/progrev-domena): Наращивание репутации нового домена для email-рассылок.
- [Выделенный IP для рассылок](https://uchecker.net/glossary/vydelennyj-ip-dlya-rassylok): Dedicated IP: когда нужен, как настроить и чем отличается от shared.
- [SPF-запись](https://uchecker.net/glossary/spf-zapis): Sender Policy Framework: DNS-запись, указывающая серверы, которым разрешено отправлять email от вашего домена.
- [DKIM-подпись](https://uchecker.net/glossary/dkim-podpis): DomainKeys Identified Mail: криптографическая подпись, подтверждающая подлинность отправителя.
- [DMARC-политика](https://uchecker.net/glossary/dmarc-politika): Политика аутентификации email: none, quarantine, reject. Как настроить и читать отчёты.
- [BIMI-запись](https://uchecker.net/glossary/bimi-zapis-glossary): Brand Indicators for Message Identification: логотип бренда рядом с письмом.
- [ARC-аутентификация](https://uchecker.net/glossary/arc-autentifikaciya): Authenticated Received Chain: сохранение аутентификации при пересылке письма.
- [DMARC alignment](https://uchecker.net/glossary/dmarc-alignment): Выравнивание доменов в SPF и DKIM для прохождения DMARC-проверки.
- [Спам-фильтр](https://uchecker.net/glossary/spam-filtr): Система фильтрации нежелательной почты: как работает и что учитывает.
- [Чёрный список DNSBL](https://uchecker.net/glossary/chyornyj-spisok-dnsbl): DNS-based Blackhole List: как работает, основные списки и как проверить.
- [Spamhaus](https://uchecker.net/glossary/spamhaus): Крупнейшая антиспам-организация: базы SBL, XBL, PBL и как попасть/выйти.
- [Контентная фильтрация email](https://uchecker.net/glossary/content-filtering): Анализ содержимого письма спам-фильтрами: слова-триггеры, HTML, ссылки.
- [Spam score](https://uchecker.net/glossary/spam-score): Числовая оценка вероятности попадания письма в спам.
- [Throttling рассылки](https://uchecker.net/glossary/throttling-rassylki): Ограничение скорости отправки email провайдерами и ESP.
- [Feedback loop](https://uchecker.net/glossary/feedback-loop-glossary): Петля обратной связи: как ISP сообщают о жалобах подписчиков на спам.
- [Inbox placement rate](https://uchecker.net/glossary/inbox-placement-rate): Процент писем, попавших во входящие, а не в спам или промоакции.
- [Bounce rate email](https://uchecker.net/glossary/bounce-rate-email-glossary): Процент отказов доставки: как считается, нормы, способы снижения.
- [Complaint rate](https://uchecker.net/glossary/complaint-rate): Процент жалоб на спам от получателей. Порог Google: 0.1%.
- [Open rate](https://uchecker.net/glossary/open-rate-glossary): Процент открытий email-рассылки: как считается, бенчмарки, ограничения.
- [Click-through rate в email](https://uchecker.net/glossary/click-through-rate-email): CTR рассылки: процент кликов по ссылкам в письме.
- [Папка Спам](https://uchecker.net/glossary/papka-spam): Куда попадают нежелательные письма и как вернуться во входящие.
- [Email deliverability](https://uchecker.net/glossary/email-deliverability-glossary): Доставляемость email: комплексный показатель способности писем попадать во входящие.
- [Google Postmaster Tools](https://uchecker.net/glossary/google-postmaster-tools): Бесплатный инструмент Google для мониторинга репутации домена и доставляемости в Gmail.
- [Seed list testing](https://uchecker.net/glossary/seed-list-testing): Тестирование доставляемости с помощью контрольных адресов у разных провайдеров.
- [Записи email-аутентификации](https://uchecker.net/glossary/email-authentication-record): DNS-записи SPF, DKIM, DMARC, BIMI: полная картина аутентификации домена.
- [Unsubscribe rate](https://uchecker.net/glossary/unsubscribe-rate): Процент отписок от рассылки: нормы, причины и как снизить.
- [List-Unsubscribe заголовок](https://uchecker.net/glossary/list-unsubscribe-header): HTTP-заголовок для быстрой отписки одним кликом. Обязателен с 2024 года.
- [Email warmup сервисы](https://uchecker.net/glossary/email-warmup-servisy): Автоматические сервисы прогрева email: как работают, риски и альтернативы.
- [Постмастер](https://uchecker.net/glossary/postmaster-glossary): Администратор почтовой системы и специальный адрес postmaster@ по RFC 5321.
- [Email spoofing](https://uchecker.net/glossary/email-spoofing): Подделка адреса отправителя email: как работает и как защититься.
- [SMTP-протокол](https://uchecker.net/glossary/smtp-protokol): Simple Mail Transfer Protocol: основной протокол отправки email. Команды, порты, ограничения.
- [IMAP-протокол](https://uchecker.net/glossary/imap-protokol): Internet Message Access Protocol: протокол чтения почты с синхронизацией.
- [POP3-протокол](https://uchecker.net/glossary/pop3-protokol): Post Office Protocol: простой протокол загрузки почты.
- [TLS-шифрование email](https://uchecker.net/glossary/tls-shifrovanje-email): Transport Layer Security: шифрование email-трафика между серверами.
- [STARTTLS](https://uchecker.net/glossary/starttls): Команда для перехода SMTP-соединения на зашифрованный канал.
- [MIME-формат](https://uchecker.net/glossary/mime-format): Multipurpose Internet Mail Extensions: стандарт вложений и HTML в email.
- [SMTP-коды ответов](https://uchecker.net/glossary/smtp-kody-otvetov): Полный справочник кодов 2xx, 4xx, 5xx: что означает каждый ответ SMTP-сервера.
- [MTA - Mail Transfer Agent](https://uchecker.net/glossary/mta-mail-transfer-agent): Агент пересылки почты: Postfix, Exim, Sendmail. Что делает и как работает.
- [MDA - Mail Delivery Agent](https://uchecker.net/glossary/mda-mail-delivery-agent): Агент локальной доставки почты: Dovecot, Procmail, Sieve.
- [MUA - почтовый клиент](https://uchecker.net/glossary/mua-pochtovyj-klient): Mail User Agent: Thunderbird, Outlook, Apple Mail и другие почтовые клиенты.
- [Почтовый сервер](https://uchecker.net/glossary/pochtovyj-server): Полная архитектура почтового сервера: MTA + MDA + хранилище.
- [Почтовая очередь](https://uchecker.net/glossary/pochtovaya-ochered): Mail queue: буфер недоставленных писем в MTA и правила повторной отправки.
- [Relay-сервер](https://uchecker.net/glossary/relay-server): Сервер ретрансляции: промежуточное звено при пересылке email.
- [Open relay](https://uchecker.net/glossary/open-relay): Открытый релей: почтовый сервер без аутентификации. Почему это опасно.
- [MX-запись](https://uchecker.net/glossary/mx-zapis): Mail Exchange record: DNS-запись, указывающая почтовый сервер домена.
- [PTR-запись](https://uchecker.net/glossary/ptr-zapis): Обратная DNS-запись: привязка IP к имени хоста для аутентификации.
- [A-запись и email](https://uchecker.net/glossary/a-zapis-i-email): Address record: когда A-запись используется для маршрутизации почты.
- [TXT-запись DNS](https://uchecker.net/glossary/txt-zapis-dns): DNS TXT record: хранение SPF, DKIM, DMARC и других текстовых записей.
- [DNS-пропагация](https://uchecker.net/glossary/dns-propagaciya): Распространение изменений DNS по серверам мира: TTL, кэширование, сроки.
- [CNAME-запись и email](https://uchecker.net/glossary/cname-zapis-i-email): Canonical Name record и ограничения использования CNAME для MX.
- [Email-заголовки](https://uchecker.net/glossary/email-zagolovki): Технические заголовки email: From, To, Subject, Date, Received и другие.
- [Return-Path](https://uchecker.net/glossary/return-path-header): Заголовок обратного пути: куда приходят bounce-уведомления.
- [Received-заголовок](https://uchecker.net/glossary/received-header): Цепочка прохождения письма через серверы: трассировка маршрута.
- [Message-ID](https://uchecker.net/glossary/message-id): Уникальный идентификатор email-сообщения по RFC 5322.
- [Envelope From и Header From](https://uchecker.net/glossary/envelope-from-i-header-from): Два адреса отправителя: технический (MAIL FROM) и видимый (From). Почему они разные.
- [ESP - Email Service Provider](https://uchecker.net/glossary/esp-email-service-provider): Платформы для email-рассылок: Mailchimp, Sendsay, Unisender и другие.
- [SMTP relay сервис](https://uchecker.net/glossary/smtp-relay-servis): Сервис отправки email через API/SMTP: SendGrid, Amazon SES, Mailgun.
- [Транзакционные письма](https://uchecker.net/glossary/transakcionnye-pisma-glossary): Автоматические email, инициированные действием пользователя: подтверждения, чеки, пароли.
- [DSN - Delivery Status Notification](https://uchecker.net/glossary/dsn-delivery-status-notification): Уведомление о статусе доставки: структура bounce-сообщений по RFC 3464.
- [Email gateway](https://uchecker.net/glossary/email-gateway): Почтовый шлюз: промежуточный сервер для фильтрации, маршрутизации и безопасности.

## Glossary (EN)

- [MX Record Check](https://uchecker.net/glossary-en/mx-record-check): How checking a domain's MX record works during email validation and what it tells you about deliverability.
- [Email Syntax Validation](https://uchecker.net/glossary-en/email-syntax-validation): Checking an email address format against RFC 5321/5322 rules: allowed characters, structure, and length.
- [Spam Traps](https://uchecker.net/glossary-en/spam-traps): What spam traps are, the three types (pristine, recycled, typo), how they reach your list, and how to keep them out.
- [Catch-all email](https://uchecker.net/glossary-en/catch-all-email): A catch-all (accept-all) domain accepts mail to any address, real or invented. Here's why that breaks SMTP validation and what to do about it.
- [Role-Based Email Address](https://uchecker.net/glossary-en/role-based-email-addresses): Role-based addresses (info@, support@, admin@) belong to a function, not a person. Why they hurt deliverability and how to handle them.
- [Disposable Email Address (DEA)](https://uchecker.net/glossary-en/disposable-email-addresses): Disposable email addresses (DEA, temp mail) live 10 minutes to a day. Learn how to detect them and why filtering them protects deliverability.
- [Greylisting](https://uchecker.net/glossary-en/greylisting): Greylisting is an anti-spam technique that temporarily rejects email from unknown senders and waits to see if the sending server retries.
- [SMTP Verification](https://uchecker.net/glossary-en/smtp-verification): SMTP verification checks whether an email address exists by connecting to the mail server without sending a message. How it works, response codes, and limits.
- [Real-time email verification](https://uchecker.net/glossary-en/real-time-email-verification): Real-time email verification checks an address the moment it is entered — via SMTP, MX, and DNS — before it reaches your database. Here's how it works.
- [Bulk Email Verification](https://uchecker.net/glossary-en/bulk-email-verification): What bulk email verification is, how batch processing works, output statuses, and when to run a list clean.
- [Double opt-in](https://uchecker.net/glossary-en/double-opt-in): Double opt-in requires a confirmation click before adding a subscriber. Learn how it works, why it cuts bounces, and when it is legally required.
- [Hard Bounce](https://uchecker.net/glossary-en/hard-bounce): A hard bounce is a permanent email delivery failure. Learn the SMTP codes, causes, deliverability risks, and how to prevent them.
- [Soft bounce](https://uchecker.net/glossary-en/soft-bounce): A soft bounce is a temporary email delivery failure. Learn what causes SMTP 4xx codes, how retry logic works, and when to remove soft-bouncing addresses.
- [Email Typo Detection](https://uchecker.net/glossary-en/email-typo-detection): How email validators catch domain typos like gmial.com and suggest corrections — algorithms, thresholds, and where to apply it.
- [Email append](https://uchecker.net/glossary-en/email-append): Email append matches your CRM records against a third-party database to fill in missing email addresses. Here's how it works, the legal risks, and the data quality problems.
- [Mailbox Existence Check](https://uchecker.net/glossary-en/mailbox-existence-check): A mailbox existence check uses SMTP to confirm whether a specific address accepts mail. How RCPT TO works, why catch-all domains complicate results, and accuracy limits.
- [Email List Hygiene](https://uchecker.net/glossary-en/email-list-hygiene): Email list hygiene means regularly removing invalid, inactive, and risky addresses. Learn which contacts to cut, how often, and why it protects your deliverability.
- [Email Deduplication](https://uchecker.net/glossary-en/email-deduplication): Email deduplication removes duplicate addresses from a mailing list. Learn why duplicates appear, how to find them, and which merge strategy to apply.
- [Email Validation API](https://uchecker.net/glossary-en/email-validation-api): An email validation API checks addresses in real time via HTTP: syntax, DNS, SMTP, disposable detection. How it works and when to use it.
- [Inactive email subscribers](https://uchecker.net/glossary-en/inactive-email-subscribers): Inactive subscribers stop opening and clicking your emails. Learn when to flag them, why they drag down deliverability, and how to run a re-engagement sequence.
- [Email List Segmentation](https://uchecker.net/glossary-en/email-list-segmentation): Email list segmentation splits subscribers into groups by behavior, demographics, or purchase stage to send more relevant campaigns and improve deliverability.
- [Poisoned Email Data](https://uchecker.net/glossary-en/poisoned-email-data): Poisoned email data: fake, malicious, and planted addresses that corrupt a mailing list. How they get in, why they matter, and how to remove them.
- [Email risk score](https://uchecker.net/glossary-en/email-risk-score): Email scoring assigns a numeric risk score to each address based on SMTP status, domain type, MX config, and risk signals. Learn what the score measures and how to act on it.
- [Email Validation Webhook](https://uchecker.net/glossary-en/email-validation-webhook): An email validation webhook is a POST request your validation service sends to your server when a check completes. Push delivery, payload structure, security, retry logic.
- [Unknown Email Status](https://uchecker.net/glossary-en/unknown-email-status): Unknown email status means the validator couldn't confirm whether a mailbox exists. Learn the causes: SMTP timeouts, greylisting, rate limiting, and how to handle these addresses.
- [Free Email Provider](https://uchecker.net/glossary-en/free-email-providers): Free email providers give users a shared-domain address at no cost. Learn how Gmail, Outlook, and Yahoo behave during SMTP verification and why provider type matters for list quality.
- [Corporate Email](https://uchecker.net/glossary-en/corporate-email): Corporate email is an address on your own domain. How it differs from free providers, why it affects deliverability, and what to watch for in B2B lists.
- [Honeypot form fields](https://uchecker.net/glossary-en/honeypot-form-fields): A honeypot field is a hidden form input that only bots fill in. Learn how it works, how to implement it correctly, and why it beats CAPTCHA for signup forms.
- [Bot Signups](https://uchecker.net/glossary-en/bot-signups): Bot signups flood your email list with fake, stolen, or random addresses. Learn how to spot them and stop them before they wreck your sender reputation.
- [Complaint Addresses](https://uchecker.net/glossary-en/complaint-addresses): Complaint addresses are subscribers who hit Spam. One complaint does more damage than a thousand unsubscribes — here is why and what to do about it.
- [Email Suppression List](https://uchecker.net/glossary-en/email-suppression-list): A suppression list is the set of addresses you must never mail: unsubscribes, spam complainers, hard bounces, and spam traps. Here's how it works and why losing it hurts.
- [DNS email validation](https://uchecker.net/glossary-en/dns-email-validation): How DNS validation works in email verification: MX, A, and TXT record checks, what each tells you, and where DNS fits in the validation pipeline.
- [Domain Age Check](https://uchecker.net/glossary-en/domain-age-check): Domain age check: how a domain's registration date signals email risk. New domains under 7 days are high-risk; learn the thresholds, WHOIS/RDAP lookup, and scoring logic.
- [GDPR and Email Marketing](https://uchecker.net/glossary-en/gdpr-email-marketing): GDPR rules for email marketing: consent requirements, subscriber rights, data processing obligations, and penalty tiers for EU violations.
- [CAN-SPAM Act](https://uchecker.net/glossary-en/can-spam-act): CAN-SPAM Act is the US federal law governing commercial email. Covers the seven requirements, opt-out rules, penalties up to $51,744 per message, and what it means for email deliverability.
- [Russian Advertising Law (38-FZ) and Email Marketing](https://uchecker.net/glossary-en/russian-advertising-law-email): Federal Law 38-FZ governs commercial email in Russia. Article 18 requires prior consent, places the proof burden on senders, and carries fines up to 500,000 RUB.
- [Single opt-in](https://uchecker.net/glossary-en/single-opt-in): Single opt-in adds subscribers instantly on form submit, no confirmation required. Learn the tradeoffs for list quality, deliverability, and compliance.
- [Confirmed opt-in](https://uchecker.net/glossary-en/confirmed-opt-in): Confirmed opt-in (COI) adds a verification click before activating a subscriber. Learn how it differs from double opt-in, when it is legally required, and why list quality improves.
- [Email Blacklist Check](https://uchecker.net/glossary-en/email-blacklist-check): What email blacklist checks are, how DNSBL lookups work, the major lists, why IPs get listed, and how to get removed.
- [Accept-all domain](https://uchecker.net/glossary-en/accept-all-domain): An accept-all domain accepts SMTP mail to any address, real or not. Learn why this makes email validation inconclusive and how to manage it in your lists.
- [Email verification accuracy](https://uchecker.net/glossary-en/email-verification-accuracy): Accuracy, precision, recall, FPR, FNR: the metrics that reveal whether an email validator is trustworthy — and how to compare services honestly.
- [Sender Reputation](https://uchecker.net/glossary-en/sender-reputation): Sender reputation is the score mailbox providers assign to your sending source. Learn what drives it, how to check it, and how to recover when it drops.
- [Sender Score](https://uchecker.net/glossary-en/sender-score): Sender Score is a 0-100 IP reputation rating from Validity. Learn what drives it, how to read the tiers, and why it differs from Gmail's own reputation system.
- [Domain Reputation](https://uchecker.net/glossary-en/domain-reputation): Domain reputation is the trust score mailbox providers assign to a sending domain. Learn what shapes it, how it differs from IP reputation, and how to check it.
- [IP Reputation](https://uchecker.net/glossary-en/ip-reputation): IP reputation is the trust score mailbox providers assign to your sending IP. Learn the difference between dedicated and shared IPs, how to check your score, and how to recover.
- [IP warming](https://uchecker.net/glossary-en/ip-warming): IP warming is the practice of gradually increasing email volume from a new IP to build sender reputation. Learn the schedule, metrics, and mistakes to avoid.
- [Domain Warming](https://uchecker.net/glossary-en/domain-warming): Domain warming: gradually ramping up email volume from a new domain to build sender reputation with mailbox providers before bulk sending.
- [Dedicated IP for email](https://uchecker.net/glossary-en/dedicated-ip-for-email): A dedicated IP gives you full control over your sender reputation. Here's when it's worth the trouble and what setup actually involves.
- [SPF Record](https://uchecker.net/glossary-en/spf-record): SPF is a DNS TXT record that authorizes mail servers to send on your domain's behalf. Learn syntax, the 10-lookup limit, common mistakes, and how SPF fits with DKIM and DMARC.
- [DKIM Signature](https://uchecker.net/glossary-en/dkim-signature): DKIM (DomainKeys Identified Mail) is a cryptographic signature added to every outbound email. Learn how it works, how to configure it, and why key rotation matters.
- [DMARC policy](https://uchecker.net/glossary-en/dmarc-policy): DMARC is a DNS record that tells mail servers what to do when SPF and DKIM fail. Covers alignment, the three policy levels, record tags, reports, and common mistakes.
- [BIMI record](https://uchecker.net/glossary-en/bimi-record): What a BIMI record is, how it works with DMARC enforcement, SVG logo requirements, VMC certificates, and which mail providers support it.
- [ARC Authentication](https://uchecker.net/glossary-en/arc-authentication): ARC preserves SPF, DKIM, and DMARC results across email forwarding hops. Defined in RFC 8617 and supported by Gmail, Microsoft 365, and Yahoo.
- [DMARC alignment](https://uchecker.net/glossary-en/dmarc-alignment): DMARC alignment ties the visible From domain to SPF and DKIM results. Without it, both protocols can pass and DMARC still fails.
- [Spam Filter](https://uchecker.net/glossary-en/spam-filter): How spam filters work: connection checks, SPF/DKIM/DMARC authentication, content scoring, and engagement signals. What causes inbox failures and how to fix them.
- [DNSBL (DNS-Based Blackhole List)](https://uchecker.net/glossary-en/dnsbl-dns-blackhole-list): What DNSBL is, how DNS-based blackhole list queries work, the major lists (Spamhaus, Barracuda, SpamCop), why IPs get listed, and how to get delisted.
- [Spamhaus](https://uchecker.net/glossary-en/spamhaus-blocklists): Spamhaus runs the SBL, XBL, PBL, and DBL blocklists used by Gmail, Outlook, and most major mail providers. Here's how they work and how to get off them.
- [Email Content Filtering](https://uchecker.net/glossary-en/email-content-filtering): Email content filtering is how spam filters analyze message body, HTML, links, and headers to assign a spam score and decide where your mail lands.
- [Spam Score](https://uchecker.net/glossary-en/spam-score): What spam score is, how filters like SpamAssassin calculate it, what raises or lowers it, and how to test your messages before sending.
- [Email Throttling](https://uchecker.net/glossary-en/email-throttling): Email throttling limits how fast a sender can deliver messages to a mail server. Why providers throttle, Gmail and Outlook limits, and how to configure your own rate.
- [Feedback loop (FBL)](https://uchecker.net/glossary-en/feedback-loop): An email feedback loop lets ISPs report spam complaints back to senders. Learn how FBL and ARF work, which providers offer them, and why your complaint rate matters.
- [Inbox placement rate](https://uchecker.net/glossary-en/inbox-placement-rate): Inbox placement rate (IPR) is the share of sent emails that land in the inbox, not spam. Learn how to measure it, what benchmarks to target, and how to improve it.
- [Email Bounce Rate](https://uchecker.net/glossary-en/email-bounce-rate): Email bounce rate: the percentage of undelivered messages. Covers hard bounce vs. soft bounce, acceptable thresholds, causes, and how to reduce bounces.
- [Complaint rate](https://uchecker.net/glossary-en/complaint-rate): Complaint rate: the share of delivered emails marked as spam. Learn the 0.1% Google threshold, FBL mechanics, and how to keep your rate low.
- [Email Open Rate](https://uchecker.net/glossary-en/email-open-rate): Email open rate: the share of delivered messages recipients opened. How tracking pixels work, Apple MPP impact, industry benchmarks, and what actually moves opens.
- [Email click-through rate (CTR)](https://uchecker.net/glossary-en/email-click-through-rate): Email CTR is the percentage of delivered messages that earned at least one click. Formula, difference from CTOR, industry benchmarks, and what actually moves it.
- [Spam Folder](https://uchecker.net/glossary-en/spam-folder): The spam folder is where mailbox providers route messages they classify as unwanted. How placement decisions work, why legitimate mail ends up there, and how to stay out.
- [Email deliverability](https://uchecker.net/glossary-en/email-deliverability): Email deliverability is how reliably your messages reach the inbox. Learn how sender reputation, SPF/DKIM/DMARC, list quality, and content filtering each affect it.
- [Google Postmaster Tools](https://uchecker.net/glossary-en/google-postmaster-tools): Google Postmaster Tools is Google's free dashboard at postmaster.google.com that shows how Gmail rates your sending domain and IP. Learn what it reports and how to act on it.
- [Seed list testing](https://uchecker.net/glossary-en/seed-list-testing): Seed list testing measures inbox placement by sending to control addresses across Gmail, Outlook, Yahoo, and more. See how it works and when to use it.
- [Email authentication records](https://uchecker.net/glossary-en/email-authentication-records): SPF, DKIM, DMARC, and BIMI are DNS records that prove a sender's identity. Required by Gmail and Yahoo for bulk senders since February 2024.
- [Unsubscribe rate](https://uchecker.net/glossary-en/email-unsubscribe-rate): Unsubscribe rate: the share of delivered emails that prompt an opt-out. Formula, industry benchmarks, causes, and how to bring the number down.
- [List-Unsubscribe Header](https://uchecker.net/glossary-en/list-unsubscribe-header): The List-Unsubscribe header lets email clients show a one-click unsubscribe button. Required for bulk senders since 2024 under Gmail and Yahoo rules.
- [Email Warmup Service](https://uchecker.net/glossary-en/email-warmup-services): Email warmup services automatically build sender reputation for new domains and IPs. Learn how they work, what the real risks are, and when manual warmup is the smarter choice.
- [Postmaster](https://uchecker.net/glossary-en/postmaster): What a postmaster is, why postmaster@ is required by RFC 5321, and how Google Postmaster Tools and similar dashboards work.
- [Email Spoofing](https://uchecker.net/glossary-en/email-spoofing): Email spoofing is forging the sender address in an email. Learn how attackers exploit SMTP, the difference between SPF, DKIM, and DMARC, and how to protect your domain.
- [SMTP Protocol](https://uchecker.net/glossary-en/smtp-protocol): SMTP (Simple Mail Transfer Protocol) is how email moves between servers. Learn commands, ports 25/465/587, response codes, and how SMTP validates addresses.
- [IMAP Protocol](https://uchecker.net/glossary-en/imap-protocol): IMAP keeps email on the server and syncs state across devices. Ports 143/993, folder flags, IDLE push, CONDSTORE resync, and when to use it over POP3.
- [POP3 protocol](https://uchecker.net/glossary-en/pop3-protocol): POP3 (RFC 1939) downloads email from a server to a local device, then deletes it. How the three session phases work, which ports to use, and when POP3 still makes sense.
- [TLS email encryption](https://uchecker.net/glossary-en/tls-email-encryption): TLS secures email in transit between servers and clients. Covers TLS 1.2 vs 1.3, STARTTLS vs implicit TLS, opportunistic vs enforced, MTA-STS, DANE, and deliverability impact.
- [STARTTLS](https://uchecker.net/glossary-en/starttls): STARTTLS upgrades a plaintext SMTP, IMAP, or POP3 connection to TLS in-place. Learn how the handshake works, downgrade attacks, MTA-STS, DANE, and Postfix config.
- [MIME Format](https://uchecker.net/glossary-en/mime-format): MIME extends email beyond plain ASCII: attachments, HTML, images, non-Latin text. Covers multipart structure, boundary, base64, quoted-printable, and Content-Type.
- [SMTP Response Codes](https://uchecker.net/glossary-en/smtp-response-codes): Three-digit SMTP response codes explained: 2xx, 3xx, 4xx, 5xx, enhanced RFC 3463 codes, and how they affect bounce handling and email validation.
- [Mail Transfer Agent (MTA)](https://uchecker.net/glossary-en/mail-transfer-agent): An MTA is server software that routes and relays email between mail servers over SMTP. Covers Postfix, Exim, mail queues, authentication, and deliverability.
- [MDA - Mail Delivery Agent](https://uchecker.net/glossary-en/mail-delivery-agent): An MDA receives mail from the MTA and places it into the recipient's mailbox. How Dovecot, Procmail, Maildir, and mbox fit into email delivery.
- [MUA (Mail User Agent)](https://uchecker.net/glossary-en/mail-user-agent): A Mail User Agent is the software you use to compose, send, and read email. Learn how Thunderbird, Outlook, and webmail clients fit into the email delivery chain.
- [Mail server](https://uchecker.net/glossary-en/mail-server): A mail server is software that receives, stores, and forwards email. Covers MTA, MDA, MUA, DNS records, and how SMTP validation interacts with the server.
- [Mail Queue](https://uchecker.net/glossary-en/mail-queue): A mail queue is the internal buffer where an MTA holds messages pending delivery. Learn how it works, why it grows, and how to monitor and manage it.
- [SMTP Relay Server](https://uchecker.net/glossary-en/smtp-relay-server): An SMTP relay server is an intermediary MTA that forwards email toward its destination. Learn smart host config, open relay risks, cloud services, and deliverability.
- [Open Relay](https://uchecker.net/glossary-en/open-relay): An open relay is a mail server that forwards email for anyone without authentication. Learn why it's a critical misconfiguration and how to fix it.
- [MX Record](https://uchecker.net/glossary-en/mx-record): MX (Mail Exchange) record: how DNS routes email to the right server, priority values, null MX (RFC 7505), common misconfigurations, and its role in email validation.
- [PTR Record](https://uchecker.net/glossary-en/ptr-record): A PTR record maps an IP address back to a hostname via reverse DNS. Learn why mail servers need one and how FCrDNS works.
- [A record and email](https://uchecker.net/glossary-en/a-record-and-email): An A record maps a domain name to an IPv4 address. Learn how A records support MX hosts, act as a delivery fallback, and interact with SPF and PTR records.
- [DNS TXT record](https://uchecker.net/glossary-en/dns-txt-record): A DNS TXT record stores arbitrary text used for SPF, DKIM, DMARC, domain ownership proofs, and more. Format, length limits, common mistakes, and email authentication explained.
- [DNS propagation](https://uchecker.net/glossary-en/dns-propagation): DNS propagation is how updated DNS records spread across recursive resolvers worldwide. TTL controls the speed, not the "24-48 hours" rule of thumb.
- [CNAME record and email](https://uchecker.net/glossary-en/cname-record-and-email): A CNAME record creates a domain alias. For email infrastructure it has hard limits: it cannot coexist with MX, breaks SPF, and affects DKIM and DMARC configurations.
- [Email Headers](https://uchecker.net/glossary-en/email-headers): Email headers are the metadata fields that control routing, authentication, and display. From, Received, DKIM-Signature, Authentication-Results, and how to read them.
- [Return-Path](https://uchecker.net/glossary-en/return-path-header): Return-Path is the email header that tells receiving servers where to send bounces. It comes from MAIL FROM in SMTP, affects SPF checks, and is central to VERP and DMARC alignment.
- [Received Header](https://uchecker.net/glossary-en/received-header): The Received header is the trace each mail server stamps on a message in transit. Learn to read the routing chain, diagnose delays, and spot forged hops.
- [Message-ID](https://uchecker.net/glossary-en/message-id): Message-ID is the RFC 5322 header that gives each email a globally unique identity. Learn how it works for deduplication, threading, and delivery debugging.
- [Envelope From and Header From](https://uchecker.net/glossary-en/envelope-from-header-from): Every email has two sender addresses. Envelope From handles bounce routing; Header From is what recipients see. Here is how they differ and why DMARC cares.
- [ESP — Email Service Provider](https://uchecker.net/glossary-en/email-service-provider): What an ESP is and how it works: SMTP relay, IP pool management, bounce handling, authentication. How to choose between shared and dedicated infrastructure.
- [SMTP relay service](https://uchecker.net/glossary-en/smtp-relay-service): An SMTP relay service is cloud infrastructure that accepts email from your app and delivers it. SendGrid, Amazon SES, Mailgun, Postmark: architecture, setup, and trade-offs.
- [Transactional email](https://uchecker.net/glossary-en/transactional-email): Transactional emails are automated messages triggered by user actions. Learn how they differ from marketing email and why they need separate sending infrastructure.
- [DSN (Delivery Status Notification)](https://uchecker.net/glossary-en/delivery-status-notification): What a Delivery Status Notification is, how RFC 3464 structures the report, what status codes mean, and how ESPs parse bounces automatically.
- [Email Gateway](https://uchecker.net/glossary-en/email-gateway): An email gateway is a server that filters and routes all inbound and outbound mail. Learn about SEG, DLP, spam filtering, encryption, and how gateways affect deliverability.

## Блог (RU)

- [Email-маркетинг для мобильных приложений: onboarding и retention](https://uchecker.net/blog/email-dlya-podpischikov-mobilnyh-prilozhenij): Push vs email, deep links, onboarding цепочки и реактивация для mobile app.
- [Обратный DNS и email: PTR-запись и FCrDNS](https://uchecker.net/blog/obratnyj-dns-i-email-ptr-fcrdns): Как настроить PTR-запись и Forward-confirmed reverse DNS для email-сервера.
- [Email-маркетинг для отелей и туризма: бронирования и лояльность](https://uchecker.net/blog/email-dlya-horeca-oteli-i-turism): Цепочки для отелей: подтверждение, pre-arrival, post-stay, программа лояльности.
- [Null MX: как защитить домен, который не принимает почту](https://uchecker.net/blog/null-mx-zapis-dlya-domenov-bez-pochty): RFC 7505 Null MX запись: зачем нужна, как настроить, влияние на валидацию.
- [Email-маркетинг для НКО и благотворительных организаций](https://uchecker.net/blog/email-dlya-nonprofitov): Сбор донатов, вовлечение волонтёров и отчётность через email-рассылки.
- [Как сохранить доставляемость при переезде на новый ESP](https://uchecker.net/blog/email-deliverability-pri-smene-esp): Миграция между ESP без потери репутации: DNS, прогрев, suppression list.
- [Email-маркетинг для медицинских услуг: HIPAA, этика и автоматизация](https://uchecker.net/blog/email-dlya-medicinskih-uslug): Рассылки для клиник и медцентров: законодательство, записи, напоминания.
- [Email benchmarks по отраслям 2026: open rate, CTR, bounce rate](https://uchecker.net/blog/email-benchmark-po-otraslyam-2026): Актуальные бенчмарки email-маркетинга по 12 отраслям: e-commerce, SaaS, B2B и другие.
- [Email-маркетинг для онлайн-курсов и edtech](https://uchecker.net/blog/email-dlya-onlajn-kursov): Цепочки для edtech: от лид-магнита до upsell. Onboarding и retention для курсов.
- [DANE для email: как настроить DNS-аутентификацию TLS](https://uchecker.net/blog/dane-dlya-email-nastrojka): DANE (DNS-Based Authentication of Named Entities): усиленная защита email-трафика.
- [Email-маркетинг для финансовых услуг: compliance и конверсия](https://uchecker.net/blog/email-dlya-finansovyh-uslug): Рассылки для банков, страховых и финтеха: регуляторные ограничения и стратегии.
- [TLS-RPT: мониторинг шифрования email-трафика](https://uchecker.net/blog/tls-rpt-nastrojka-i-monitoring): Как настроить TLS-RPT для получения отчётов о проблемах с шифрованием.
- [Email-маркетинг для недвижимости: стратегия и автоматизация](https://uchecker.net/blog/email-marketing-dlya-nedvizhimosti): Лиды, просмотры, сделки - email-цепочки для риэлторов и агентств.
- [Email deliverability чек-лист перед запуском нового домена](https://uchecker.net/blog/email-deliverability-checklist-pered-zapuskom): 30 пунктов проверки перед первой рассылкой с нового домена.
- [CTA-кнопка в email: дизайн, текст и размещение](https://uchecker.net/blog/cta-button-dizajn-email): Bulletproof buttons, цвета, тексты, A/B тесты - всё про CTA в email.
- [AI для тестирования email-контента: автоматический QA](https://uchecker.net/blog/ai-email-content-testing): Как AI проверяет контент перед отправкой: тон, спам-слова, рендеринг.
- [Email footer: что обязательно включить и как оформить](https://uchecker.net/blog/email-footer-luchshie-praktiki): Юридические требования, отписка, контакты, соцсети - анатомия футера.
- [Предиктивная оптимизация отправки email: beyond STO](https://uchecker.net/blog/predictive-email-send-optimization): AI определяет не только время, но и канал, частоту и контент.
- [GIF в email: размер, оптимизация и поддержка клиентами](https://uchecker.net/blog/email-gif-best-practices): Технические ограничения GIF в email: вес, fallback, Outlook.
- [AI-инструменты для автоматической сегментации email](https://uchecker.net/blog/ai-email-segmentation-tools): Klaviyo, ActiveCampaign, Drip: как AI строит сегменты автоматически.
- [Многоязычные email-рассылки: локализация и технические нюансы](https://uchecker.net/blog/email-lokalizaciya-mnogoiyazychnye): Как отправлять рассылки на нескольких языках: сегментация, контент, верстка.
- [AI для оптимизации тем писем: инструменты и подход](https://uchecker.net/blog/ai-subject-line-optimization): Как AI генерирует и тестирует subject lines. Phrasee, Jasper, Mailchimp AI.
- [Email-маркетинг для ресторанов и кафе: практический гайд](https://uchecker.net/blog/email-dlya-restoranov-i-kafe): Бронирования, меню, акции, лояльность - email для HoReCa.
- [Pre-send QA чек-лист: 20 проверок перед отправкой рассылки](https://uchecker.net/blog/pre-send-qa-checklist): Системная проверка перед каждой отправкой: контент, техника, юридика.
- [Карта customer journey для email: как построить и использовать](https://uchecker.net/blog/customer-journey-email-mapping): Mapping touchpoints на воронку: от awareness до advocacy.
- [Шифрование email: S/MIME, PGP и когда они нужны](https://uchecker.net/blog/email-encryption-smime-pgp): Как работает end-to-end шифрование email, практическое применение.
- [Gamification в email: интерактив, который повышает engagement](https://uchecker.net/blog/email-gamification-primery): Scratch-cards, quiz, колесо удачи, таймеры обратного отсчёта.
- [Email в dark mode: как сделать чтобы не сломалось](https://uchecker.net/blog/email-dark-mode-dizajn): CSS prefers-color-scheme, прозрачные PNG, цвета для тёмной темы.
- [Как считать ROI email-маркетинга: формулы и примеры](https://uchecker.net/blog/email-roi-kak-schitat): Формулы расчета ROI, атрибуция, типичные ошибки в подсчетах.
- [Email compliance audit: как проверить рассылки на соответствие](https://uchecker.net/blog/email-compliance-audit): Чек-лист проверки email-рассылок на GDPR, CAN-SPAM, ФЗ-38, ФЗ-152.
- [Plain text vs HTML email: когда что выбрать](https://uchecker.net/blog/plain-text-vs-html-email): Плюсы и минусы каждого формата. Когда plain text побеждает HTML.
- [SMTP relay сервисы: сравнение SendGrid, Amazon SES, Mailgun](https://uchecker.net/blog/smtp-relay-sravnenie-servisov): Цены, лимиты, API, доставляемость - честное сравнение.
- [Автоматизация email-гигиены через API: архитектура и код](https://uchecker.net/blog/email-gigiena-avtomatizaciya-api): Как настроить автоматическую очистку базы: cron, webhook, API.
- [Email-опросы и сбор обратной связи: форматы и инструменты](https://uchecker.net/blog/email-opros-i-feedback): NPS, CSAT, inline-опросы, интеграция с Typeform/Google Forms.
- [Как работает трекинг открытий и кликов в email](https://uchecker.net/blog/click-open-tracking-mekhanika): Пиксели, редиректы, ограничения MPP. Техническая механика.
- [Видео в email: как использовать без потери доставляемости](https://uchecker.net/blog/video-v-email-kak-ispolzovat): GIF-превью, play-button, fallback - техники для video email.
- [Как пересылка email ломает аутентификацию и что с этим делать](https://uchecker.net/blog/email-forwarding-vliyanie-na-auth): SPF fail при forward, DKIM-сохранение, ARC-решение.
- [Email-маркетинг для продавцов на маркетплейсах](https://uchecker.net/blog/email-dlya-marketplace-sellerov): Как использовать email для Wildberries, Ozon и Amazon-селлеров.
- [Email-тестирование: Litmus, Email on Acid и бесплатные альтернативы](https://uchecker.net/blog/email-testing-tools-litmus-acid): Обзор инструментов для тестирования email перед отправкой.
- [Storytelling в email: как рассказывать истории в рассылках](https://uchecker.net/blog/email-storytelling-tehniki): Техники нарративного email-маркетинга с примерами.
- [Gmail Annotations: как добавить промо-карточки и предложения](https://uchecker.net/blog/gmail-annotations-schema): Schema.org разметка для rich results в Gmail Promotions tab.
- [Сезонные email-кампании: черная пятница, новый год и другие](https://uchecker.net/blog/seasonal-email-kampanii): Календарь сезонных кампаний с таймингами подготовки.
- [Мобильная оптимизация email: что проверить перед отправкой](https://uchecker.net/blog/mobile-email-optimizaciya): 70% открывают на телефоне. Шрифты, кнопки, ширина, прехедер.
- [Email-кампания для запуска продукта: пошаговый план](https://uchecker.net/blog/product-launch-email-kampaniya): Pre-launch, launch day, follow-up - как выстроить email-кампанию для нового продукта.
- [Email-клиенты в 2026: доли рынка и что это значит для верстки](https://uchecker.net/blog/email-klient-market-share-2026): Apple Mail, Gmail, Outlook - кто лидирует и как это влияет на дизайн.
- [Sunset policy: когда и как удалять неактивных подписчиков](https://uchecker.net/blog/sunset-policy-dlya-email-bazy): Правила удаления неактивных: сроки, предупреждения, автоматизация.
- [MTA-STS: как защитить email от downgrade-атак](https://uchecker.net/blog/mta-sts-nastrojka): Настройка MTA-STS для принудительного TLS между серверами.
- [Re-permission кампания: как запросить согласие заново](https://uchecker.net/blog/re-permission-kampaniya): Когда и как проводить re-permission: после GDPR, после паузы, после миграции.
- [Как email выглядит в разных клиентах: тестирование и совместимость](https://uchecker.net/blog/email-rendering-v-raznyh-klientah): Gmail, Outlook, Apple Mail, Яндекс - различия рендеринга и как тестировать.
- [Контент-календарь для email-рассылок: как планировать на месяц](https://uchecker.net/blog/email-content-calendar-planirovanie): Шаблон контент-плана для email-маркетинга с примерами.
- [Email list decay: как быстро устаревает база и что с этим делать](https://uchecker.net/blog/email-list-decay-statistika): Статистика устаревания email-базы: 22-30% в год. Как противодействовать.
- [Email preference center: как дать подписчику выбор](https://uchecker.net/blog/email-preference-center): Центр управления подписками: что показывать, как снизить отписки.
- [Как распознать фишинговое письмо: технический разбор](https://uchecker.net/blog/phishing-detection-v-email): SPF/DKIM/DMARC проверка, URL-анализ, red flags в заголовках.
- [Email + SMS: как интегрировать каналы для максимального охвата](https://uchecker.net/blog/email-sms-integratsiya): Когда использовать email, когда SMS, как комбинировать.
- [Анализ заголовков email: как читать и диагностировать проблемы](https://uchecker.net/blog/email-header-analysis-guide): Разбор Received, Authentication-Results, X-headers для диагностики.
- [Реферальная программа через email: как запустить](https://uchecker.net/blog/referalnaya-programma-email): Email-цепочки для реферальных программ: приглашение, напоминание, награда.
- [Custom tracking domain: зачем и как настроить](https://uchecker.net/blog/custom-tracking-domain-nastrojka): Собственный домен для трекинга кликов и открытий: влияние на доставляемость.
- [Birthday email и юбилейные рассылки: настройка и примеры](https://uchecker.net/blog/birthday-email-avtomatizaciya): Как автоматизировать поздравительные письма и увеличить LTV.
- [Доставляемость в Яндекс.Почте: особенности и настройка](https://uchecker.net/blog/yandex-pochta-dostavlyaemost): Специфика Яндекс.Почты: postmaster, фильтры, требования.
- [Win-back кампания: как вернуть ушедших клиентов](https://uchecker.net/blog/win-back-kampaniya-vozvrat-klientov): Стратегия реактивации ушедших: тайминг, контент, офферы.
- [Доставляемость в Mail.ru: особенности и рекомендации](https://uchecker.net/blog/mail-ru-dostavlyaemost-osobennosti): Специфика Mail.ru: фильтры, reputation, чего не делать.
- [Email-маркетинг для вебинаров и событий: полный цикл](https://uchecker.net/blog/email-dlya-vebinarov-i-sobytij): Приглашение, напоминание, follow-up, запись - цепочка для событий.
- [Требования Yahoo к отправителям email в 2026](https://uchecker.net/blog/yahoo-sender-requirements-2026): Что Yahoo требует от массовых отправителей: auth, FBL, unsubscribe.
- [Как делать newsletter, который читают: стратегия и формат](https://uchecker.net/blog/newsletter-strategiya-i-format): Частота, формат, контент и метрики для регулярной рассылки.
- [Требования Gmail к отправителям в 2026 году](https://uchecker.net/blog/gmail-sender-guidelines-2026): Актуальные требования Gmail: аутентификация, порог жалоб, one-click unsubscribe.
- [Email в программах лояльности: стратегия и автоматизация](https://uchecker.net/blog/programma-loyalnosti-email): Как использовать email для удержания через баллы, уровни и персональные предложения.
- [Apple Mail Privacy Protection: как это влияет на email-маркетинг](https://uchecker.net/blog/apple-mail-privacy-protection-vliyanie): Что MPP делает с open rate и как адаптировать стратегию.
- [Post-purchase email: серия писем после покупки](https://uchecker.net/blog/post-purchase-email-seriya): Подтверждение, доставка, отзыв, повторная покупка - 4 письма после заказа.
- [SPF flattening: как обойти лимит в 10 DNS-запросов](https://uchecker.net/blog/spf-flattening-kak-obojti-limit): Что такое SPF flattening, инструменты и ручная настройка.
- [Брошенная корзина: email-стратегии возврата покупателей](https://uchecker.net/blog/broshennaya-korzina-email-strategii): Цепочка из 3 писем для возврата брошенных корзин с таймингами и примерами.
- [Ротация DKIM-ключей: зачем, когда и как](https://uchecker.net/blog/dkim-rotaciya-klyuchej): Как и зачем менять DKIM-ключи, расписание ротации, автоматизация.
- [Welcome email: лучшие практики и примеры цепочек](https://uchecker.net/blog/welcome-email-luchshie-praktiki): Как создать welcome-серию, которая конвертирует: структура, тайминг, контент.
- [Как построить data pipeline для email-аналитики](https://uchecker.net/blog/kak-postroit-data-pipeline-dlya-email-analitiki): Webhook, ETL, ClickHouse, Grafana.
- [Email-база с нуля: пошаговый план на первые 1000 подписчиков](https://uchecker.net/blog/email-baza-s-nulya-poshagovyj-plan-na-pervye-1000-podpischikov): Как собрать первые 1000 email-подписчиков с нуля.
- [BIMI-запись: как добавить логотип компании в email](https://uchecker.net/blog/bimi-zapis-logo-v-email-kak-nastroit): BIMI: настройка логотипа, SVG формат, VMC сертификат.
- [Тренды email-маркетинга в 2026 году: что работает прямо сейчас](https://uchecker.net/blog/email-marketing-trendy-2026): AMP-письма, AI-генерация, zero-party data, интерактивный контент.
- [AI в борьбе со спамом: как работают современные спам-фильтры](https://uchecker.net/blog/ai-v-borbe-so-spamom-kak-rabotayut-sovremennye-filtry): Как спам-фильтры используют AI и machine learning.
- [10 ошибок email-маркетинга, которые убивают доставляемость](https://uchecker.net/blog/email-marketing-oshibki-kotorye-ubivayut-dostavlyaemost): 10 ошибок, из-за которых падает доставляемость.
- [Email-валидация на уровне инфраструктуры: milter, Postfix](https://uchecker.net/blog/email-validaciya-na-urovne-infrastruktury-milter-postfix): Milter-протокол, Postfix policy server, кастомные фильтры.
- [Подписчик отправил вас в спам: как вернуться в инбокс](https://uchecker.net/blog/kak-vernut-podpischikov-iz-spama-v-inbox): Feedback loop, complaint rate и шаги по возврату из спама.
- [Репутация IP vs репутация домена: что важнее в 2026 году](https://uchecker.net/blog/reputaciya-ip-vs-reputaciya-domena-chto-vazhnee): IP-репутация vs доменная репутация. Dedicated vs shared IP.
- [Доступность email-писем: как сделать рассылку для всех](https://uchecker.net/blog/email-dostupnost-accessibility-pisem): Alt-тексты, контрастность, семантическая разметка, screen reader.
- [AI-персонализация email в реальном времени](https://uchecker.net/blog/ai-personalizaciya-email-v-realnom-vremeni): Сбор данных, модели рекомендаций, архитектура.
- [Как выбрать сервис email-рассылок в 2026 году](https://uchecker.net/blog/kak-vybrat-servis-email-rassilok-2026): Критерии выбора ESP. Обзор Unisender, Sendsay, Mailchimp, Brevo.
- [Валидация email на Node.js: библиотеки, сервисы и best practices](https://uchecker.net/blog/node-js-email-validation-biblioteki-i-servisy): Библиотеки для валидации email в Node.js.
- [Email-рассылки для B2B: особенности, стратегии и примеры](https://uchecker.net/blog/email-rassilki-dlya-b2b-osobennosti-i-strategii): B2B email-маркетинг: длинный цикл сделки, lead nurturing.
- [Google Postmaster Tools и Yahoo Postmaster: настройка и отчёты](https://uchecker.net/blog/postmaster-tools-google-yahoo-nastrojka-i-analitika): Настройка и чтение отчётов Postmaster Tools.
- [Как не попасть во вкладку Промоакции Gmail](https://uchecker.net/blog/kak-ne-popast-v-promotions-gmail): Почему письма в Промоакциях и как попасть в основную вкладку.
- [Интеграция email-валидации с CRM: Bitrix24, amoCRM, HubSpot](https://uchecker.net/blog/integraciya-email-validacii-s-crm-sistemami): Валидация email в CRM: Bitrix24, amoCRM, HubSpot.
- [Email-маркетинг для SaaS: стратегия, цепочки и метрики](https://uchecker.net/blog/email-marketing-dlya-saas-strategiya-i-cepochki): Onboarding, trial-to-paid, churn prevention для SaaS.
- [Send time optimization: как AI подбирает идеальное время отправки](https://uchecker.net/blog/send-time-optimization-s-pomoshhyu-ai): Алгоритмы STO изнутри: данные, модели, реализация.
- [Лучшее время для отправки email-рассылок: данные и эксперименты](https://uchecker.net/blog/luchshee-vremya-dlya-otpravki-email-rassilok): Анализ лучшего времени и дня для отправки email.
- [AI для прогнозирования оттока подписчиков: модели и практика](https://uchecker.net/blog/ai-dlya-prognozirovaniya-ottoka-podpischikov): Как AI-модели предсказывают отток подписчиков.
- [Как очистить email-базу после долгого перерыва в рассылках](https://uchecker.net/blog/kak-ochistit-email-bazu-posle-dolgogo-pereryva): План очистки email-базы после 6+ месяцев без рассылок.
- [Транзакционные письма vs маркетинговые: разница и правила](https://uchecker.net/blog/transakcionnye-pisma-vs-marketingovye-raznica-i-pravila): Чем транзакционные письма отличаются от маркетинговых.
- [Триггерные email-рассылки: 12 типов с примерами и шаблонами](https://uchecker.net/blog/triggernye-email-rassilki-tipy-i-primery): 12 типов триггерных email-рассылок с примерами.
- [Webhook для email-событий: настройка, обработка и отладка](https://uchecker.net/blog/webhook-dlya-email-sobytij-nastrojka-i-obrabotka): Webhook для delivery, bounce, open, click. Примеры на Node.js.
- [Что такое email API и зачем он нужен](https://uchecker.net/blog/chto-takoe-email-api-i-zachem-on-nuzhen): Что такое email API, как работает и когда нужна интеграция.
- [AI-генерация email-контента: инструменты, промпты и ограничения](https://uchecker.net/blog/ai-generaciya-email-kontenta-instrumenty-i-prompty): AI для создания email-контента: инструменты и промпты.
- [Как писать тексты email-рассылок, которые читают до конца](https://uchecker.net/blog/kak-pisat-tekst-email-rassylok-kotorye-chitayut): Копирайтинг для email: структура, CTA, тон.
- [GDPR и email-маркетинг: руководство для работы с EU](https://uchecker.net/blog/gdpr-i-email-marketing-rukovodstvo-dlya-raboty-s-eu): GDPR в email-маркетинге: lawful basis, сбор согласия.
- [Email-рассылки и ФЗ-152: что нужно знать о персональных данных](https://uchecker.net/blog/email-rassilki-i-fz-152-chto-nuzhno-znat): ФЗ-152, закон о рекламе, получение согласия, штрафы.
- [Как почтовые провайдеры решают, доставить письмо или отправить в спам](https://uchecker.net/blog/kak-rassilochnyj-servis-vybiraet-komu-dostavit-pismo): Как работают спам-фильтры Gmail, Mail.ru и Яндекс.Почты.
- [Прогрев домена и IP для email-рассылок: полный гайд](https://uchecker.net/blog/warm-up-domena-i-ip-dlya-email-rassilok): План прогрева с расписанием на 4 недели.
- [Верстка адаптивных email-писем: HTML, CSS и подводные камни](https://uchecker.net/blog/vyorstka-adaptivnyh-email-pisem-html-css): Ограничения почтовых клиентов, inline CSS, media queries.
- [Дизайн email-писем: лучшие практики и тренды 2026](https://uchecker.net/blog/email-dizajn-luchshie-praktiki-2026): Адаптивная верстка, темная тема, интерактивные элементы.
- [A/B тестирование email-рассылок: что тестировать и как анализировать](https://uchecker.net/blog/ab-testirovanie-email-rassilok): Руководство по A/B тестированию email.
- [Метрики email-маркетинга: что отслеживать и какие показатели нормальные](https://uchecker.net/blog/email-marketing-metriki-kotorye-nuzhno-otslezhivat): Ключевые метрики email-маркетинга с бенчмарками.
- [Валидация email на Python: библиотеки, примеры кода и подводные камни](https://uchecker.net/blog/python-email-validation-biblioteki-i-primery): Python-библиотеки для валидации email.
- [Персонализация email-рассылок: больше чем просто имя в теме](https://uchecker.net/blog/personalizaciya-email-rassilok-bolshe-chem-imya): От merge tags до AI-рекомендаций.
- [Bulk email validation через API: оптимизация для больших списков](https://uchecker.net/blog/bulk-email-validation-api-optimizaciya-bolshih-spiskov): Валидация миллионов email через API: батчинг, rate limits.
- [Черные списки email (blacklist): как проверить и выйти](https://uchecker.net/blog/chto-takoe-chyornyj-spisok-email-i-kak-proverit): Email-блэклисты, проверка IP/домена, инструкция по удалению.
- [Double opt-in vs single opt-in: что лучше для вашей базы](https://uchecker.net/blog/double-opt-in-vs-single-opt-in): Сравнение double opt-in и single opt-in.
- [Как создать лид-магнит для сбора email-подписчиков](https://uchecker.net/blog/kak-sozdat-lead-magnit-dlya-sbora-email): 12 типов лид-магнитов с примерами.
- [Регулярные выражения для проверки email: полный разбор паттернов](https://uchecker.net/blog/regulyarnye-vyrazheniya-dlya-proverki-email): Regex-паттерны для валидации email.
- [Почему подписчики отписываются и как это предотвратить](https://uchecker.net/blog/pochemu-podpischiki-otpisyvayutsya-i-kak-eto-predotvratit): Причины отписок и снижение unsubscribe rate.
- [Мониторинг доставляемости email: инструменты и ключевые метрики](https://uchecker.net/blog/monitoring-deliverability-instrumenty-i-metriki): Метрики доставляемости и инструменты мониторинга.
- [Что такое email deliverability и от чего она зависит](https://uchecker.net/blog/chto-takoe-email-deliverability-prostym-yazykom): Что такое email deliverability, факторы влияния.
- [Email-воронка продаж: как настроить автоматические цепочки](https://uchecker.net/blog/email-voronka-prodazh-avtomaticheskie-cepochki): Welcome-серия, нурсеринг, конверсия и retention.
- [Email-маркетинг для интернет-магазина: полное руководство](https://uchecker.net/blog/email-marketing-dlya-internet-magazina): Гайд по email-маркетингу для e-commerce.
- [MX-записи: что это, как проверить и зачем нужны для валидации email](https://uchecker.net/blog/mx-zapisi-chto-eto-i-kak-proverit): MX-записи DNS: как работают, как проверить через dig/nslookup.
- [Как написать тему письма, которую откроют: 15 формул](https://uchecker.net/blog/kak-napisat-effektivnuyu-temu-pisma): 15 рабочих формул для тем email-рассылок.
- [Автоматическая обработка bounce-писем: webhook, логи и скрипты](https://uchecker.net/blog/obrabotka-bounce-pisem-avtomatizaciya): Автоматизация обработки bounce: webhook, парсинг логов.
- [Hard bounce и soft bounce: в чём разница и что делать](https://uchecker.net/blog/chto-takoe-hard-bounce-i-soft-bounce): Разница между hard bounce и soft bounce. SMTP-коды.
- [Интеграция email-валидации в формы регистрации](https://uchecker.net/blog/integraciya-email-validacii-v-formy-registracii): Real-time валидация email в формах. Примеры кода на JavaScript.
- [Open rate email-рассылки: что это такое и как увеличить](https://uchecker.net/blog/open-rate-email-chto-eto-kak-uvelichit): Что такое open rate и 10 способов повысить открываемость.
- [Как восстановить репутацию отправителя: план действий](https://uchecker.net/blog/kak-vosstanovit-reputaciyu-otpravitelya): План восстановления после попадания в черные списки.
- [Что такое репутация отправителя email и как её проверить](https://uchecker.net/blog/chto-takoe-email-reputation-otpravitelya): От чего зависит репутация отправителя и как её проверить.
- [Продвинутая сегментация email: RFM-анализ, поведение и lifecycle](https://uchecker.net/blog/prodvinutaya-segmentaciya-email-dlya-marketologov): RFM-модель, поведенческие триггеры, lifecycle-стадии.
- [Сегментация email-базы: руководство для начинающих](https://uchecker.net/blog/email-segmentaciya-rukovodstvo-dlya-nachinayuschih): Как начать сегментировать подписчиков даже с небольшой базой.
- [Настройка SPF, DKIM и DMARC: пошаговая инструкция для разработчика](https://uchecker.net/blog/nastrojka-spf-dkim-dmarc-poshagovaya-instrukciya): Техническое руководство по настройке через DNS.
- [Что такое SPF, DKIM и DMARC простым языком](https://uchecker.net/blog/chto-takoe-spf-dkim-dmarc-prostym-yazykom): Три протокола аутентификации email без жаргона.
- [Автоматическая валидация списков: ИИ против правил](https://uchecker.net/blog/avtomaticheskaya-validaciya-ii-vs-pravila): Сравниваем классический подход на основе regex и MX-проверок с новыми AI-моделями, которые предсказывают валидность адреса.
- [Как ИИ меняет email-маркетинг в 2026 году](https://uchecker.net/blog/kak-ii-menyaet-email-marketing-2026): Обзор ключевых AI-инструментов, которые автоматизируют сегментацию, персонализацию и A/B-тесты в email-кампаниях.
- [Гигиена email-базы: чек-лист на 2026 год](https://uchecker.net/blog/gigiena-email-bazy-chek-list-2026): Пошаговый чек-лист для очистки и поддержания здоровой базы подписчиков - с учётом новых требований почтовых провайдеров.
- [Как повысить доставляемость писем: 10 проверенных стратегий](https://uchecker.net/blog/kak-povysit-dostavlyaemost-pisem): От настройки SPF/DKIM/DMARC до прогрева домена - разбираем стратегии, которые реально влияют на inbox rate.
- [Почему письма попадают в спам и как это исправить](https://uchecker.net/blog/pochemu-pisma-popadayut-v-spam): Разбираемся, почему рассылки уходят в спам. Чек-лист из 7 шагов, которые можно выполнить за 30 минут - без технического жаргона.
- [Предиктивная аналитика в email-маркетинге: что стало возможным](https://uchecker.net/blog/prediktivnaya-analitika-v-email-marketinge): Как машинное обучение помогает предсказывать отписки, оптимальное время отправки и lifetime value подписчика.
- [Бесплатные программы для проверки базы email адресов](https://uchecker.net/blog/besplatnye-programmy-proverki-bazy): Free tiers сервисов, open-source решения и их ограничения. Когда хватит бесплатного, а когда нужен платный.
- [Что такое bounce rate в email-рассылках и как его снизить](https://uchecker.net/blog/chto-takoe-bounce-rate-v-email-rassilkah): Разбираемся, что такое bounce rate, чем hard bounce отличается от soft bounce, что значат коды ошибок SMTP и как снизить процент отказов.
- [Сравнение сервисов проверки email: на что обращать внимание](https://uchecker.net/blog/sravnenie-servisov-proverki-email): 8 критериев выбора валидатора: точность, скорость, цена, API, catch-all, GDPR, поддержка, бесплатный тариф.
- [Как выбрать email валидатор для бизнеса](https://uchecker.net/blog/kak-vybrat-email-validator): 3 сценария выбора валидатора: стартап, средний бизнес, enterprise. Приоритеты, red flags и практические советы.
- [Лучшие сервисы валидации email: обзор и сравнение 2026](https://uchecker.net/blog/luchshie-servisy-validacii-email): Честный обзор 8 сервисов валидации: ZeroBounce, NeverBounce, Hunter, uChecker и другие. Цены, скорость, точность.
- [Законна ли парсинговая база email?](https://uchecker.net/blog/zakonna-li-parsingovaya-baza-email): GDPR, ФЗ-152, CAN-SPAM о собранных и купленных базах. Реальные штрафы, серая зона B2B и роль валидации.
- [uChecker API - руководство для разработчиков](https://uchecker.net/blog/uchecker-api-rukovodstvo-dlya-razrabotchikov): Пошаговый гайд по uChecker API: авторизация, валидация email, bulk-проверка, polling задач. Примеры на curl, Python, Node.js.
- [Как найти email директора / ЛПР](https://uchecker.net/blog/kak-najti-email-direktora-lpr): 6 методов поиска email лиц, принимающих решения: от LinkedIn до угадывания паттернов. Этичность и законность каждого способа.
- [Холодные email рассылки: правила и подводные камни](https://uchecker.net/blog/holodnye-email-rassilki-pravila): Что считается cold email, легальность в разных юрисдикциях (CAN-SPAM, GDPR, ФЗ-152), техника и почему валидация критична.
- [Подготовка базы email к рассылке](https://uchecker.net/blog/podgotovka-bazy-email-k-rassilke): От грязной базы к чистой за 5 шагов: дедупликация, синтаксическая чистка, валидация, сегментация и прогрев.
- [Как собрать базу для email рассылки](https://uchecker.net/blog/kak-sobrat-bazu-dlya-email-rassilki): Легальные способы сбора базы подписчиков, риски парсинга и покупки баз, и почему валидация обязательна после любого метода сбора.
- [Как работает валидатор email технически](https://uchecker.net/blog/kak-rabotaet-validator-email): Пошагово разбираем 6 этапов валидации: от синтаксической проверки до catch-all детекции. С примерами SMTP-диалогов и DNS-запросов.
- [Как найти и удалить спам-ловушки из базы](https://uchecker.net/blog/kak-najti-spam-lovushki-v-baze): Признаки наличия спам-ловушек в базе, пошаговый процесс очистки и превентивные меры для защиты репутации отправителя.
- [Реактивация спящих подписчиков email](https://uchecker.net/blog/reaktivaciya-spyaschih-podpischikov): Когда реактивировать, а когда удалять. Цепочка из 4 писем с примерами тем и таймингом. Валидация до реактивации.
- [Что такое валидация email: полный гайд для начинающих](https://uchecker.net/blog/chto-takoe-validaciya-email): Что такое валидация почты, как она работает, зачем нужна и когда без неё точно не обойтись. Разбираем типы плохих адресов и процесс проверки.
- [Почему важна проверка электронной почты: хорошее, плохое и уродливое](https://uchecker.net/blog/pochemu-vazhna-proverka-elektronnoj-pochty): Объясняем важность верификации email адресов.
- [Секреты проверки электронной почты](https://uchecker.net/blog/sekrety-proverki-elektronnoj-pochty): Советы по поддержанию актуальных списков рассылки.
- [Что входит в состав почтовика для организации?](https://uchecker.net/blog/chto-vhodit-v-sostav-pochtovika): Разбираем составные части корпоративного почтового сервера.

## Blog (EN)

- [How to Find and Remove Spam Traps From Your Email List](https://uchecker.net/blog-en/how-to-find-spam-traps): Warning signs that spam traps are hiding in your list, a step-by-step cleanup process, and preventive measures to protect your sender reputation.
- [Email List Verification: The Good, the Bad, and the Ugly](https://uchecker.net/blog-en/why-email-verification-matters): What email validation actually delivers, what a dirty list costs you, and the horror scenarios that hit senders who skip it. Real numbers, real case study.
- [How an Email Validator Works: 6 Stages Explained](https://uchecker.net/blog-en/how-email-validator-works): From RFC 5322 syntax to SMTP handshake, catch-all detection, and disposable domains: a technical walkthrough of every stage a real email validator runs.
- [How to Build an Email List: Legitimate Methods, Gray Areas, and Why Validation Comes Last](https://uchecker.net/blog-en/how-to-build-an-email-list): Opt-in forms, lead magnets, webinars, scraping, buying lists — what actually works, what kills your domain, and why you need to validate every list you collect.
- [How to Prepare Your Email List Before Sending](https://uchecker.net/blog-en/preparing-email-list-for-sending): Five steps from raw CSV to send-ready list: deduplication, syntax cleaning, email validation, segmentation, and domain warm-up. Cut bounce rate from 12% to under 2%.
- [Cold Email Outreach: Rules, Risks, and What Actually Works](https://uchecker.net/blog-en/cold-email-outreach-rules): CAN-SPAM, GDPR, domain warm-up, bounce thresholds, spam traps — the full picture for cold email senders who want deliverability, not bans.
- [How to Find a Decision-Maker's Email Address: 6 Methods That Work](https://uchecker.net/blog-en/how-to-find-decision-maker-email): Six practical ways to find a CEO or B2B decision-maker's real email: LinkedIn, Hunter.io, address pattern guessing, site scraping, WHOIS, and social profiles. With validation.
- [Is a Scraped Email List Legal? GDPR, CAN-SPAM, and B2B](https://uchecker.net/blog-en/is-scraped-email-list-legal): Scraped email lists and the law: GDPR, CAN-SPAM, and the B2B grey zone explained. Real fines, when scraping is defensible, and why validation still matters.
- [Reactivating Inactive Email Subscribers: A Step-by-Step Strategy](https://uchecker.net/blog-en/reactivating-inactive-email-subscribers): How to win back dormant subscribers: a 4-email sequence, subject line examples, and success metrics. Why validating your list before reactivation is non-negotiable.
- [Best Email Validation Services: Compared for 2026](https://uchecker.net/blog-en/best-email-validation-services): We tested 8 email validation services on 50K addresses: ZeroBounce, NeverBounce, Hunter, Kickbox, Debounce, Clearout, EmailListVerify, uChecker. Pricing, speed, API, pros and cons.
- [Email Validation Service Comparison: 8 Criteria That Matter](https://uchecker.net/blog-en/email-validation-service-comparison): Eight criteria for picking an email validation service: accuracy, speed, pricing, API, catch-all handling, GDPR, support, and free tier. A brand-agnostic checklist.
- [How to Choose an Email Validation Service for Your Business](https://uchecker.net/blog-en/how-to-choose-email-validation-service): Practical guide to picking an email validation service: criteria for startups, mid-size teams, and enterprise. What to test before you buy, and red flags to avoid.
- [Free Email List Validation Tools: What They Can (and Can't) Do](https://uchecker.net/blog-en/free-email-list-validation-tools): Free tiers, open-source libraries, and their real limits. A plain look at what each option delivers before you send.
- [Email Bounce Rate: Hard Bounce vs Soft Bounce Explained](https://uchecker.net/blog-en/email-bounce-rate-explained): Learn what email bounce rate is, how hard and soft bounces differ, what SMTP error codes mean, and seven concrete steps to bring your bounce rate under 2%.
- [uChecker API Developer Guide: Auth, Validation & Bulk Jobs](https://uchecker.net/blog-en/uchecker-api-developer-guide): Complete uChecker API walkthrough: authentication, single and bulk email validation, task polling, result retrieval. Working examples in curl, Python, and Node.js.
- [Why Emails Go to Spam (and How to Fix It)](https://uchecker.net/blog-en/why-emails-go-to-spam): About 20% of legitimate emails never reach the inbox. Here are the 7 most common causes, the new Google/Yahoo rules, and a 30-minute checklist to fix it.
- [What Is Email Validation: A Complete Beginner's Guide](https://uchecker.net/blog-en/what-is-email-validation): What email validation is, how it works, and when you actually need it. Covers bad address types, the three-step verification process, and list hygiene basics.
- [Predictive Analytics in Email Marketing: What Actually Works](https://uchecker.net/blog-en/predictive-analytics-email-marketing): How ML models predict unsubscribes, optimize send times, and score lifetime value — and why none of it works without a clean list first.
- [10 Email Deliverability Strategies That Actually Work](https://uchecker.net/blog-en/email-deliverability-strategies): SPF/DKIM/DMARC setup, domain warm-up, list validation, sunset policy, and ESP selection — 10 concrete strategies tested on real sending campaigns.
- [Email List Hygiene Checklist for 2026](https://uchecker.net/blog-en/email-list-hygiene-checklist-2026): 8-point checklist to clean your email list: validate addresses, remove hard bounces, kill role-based addresses, detect spam traps, and automate it all.
- [Email List Validation: Rules-Based vs AI — Honest Comparison](https://uchecker.net/blog-en/email-validation-rules-vs-ai): Regex, MX, SMTP or an ML model? We break down both approaches to email list validation — where each works, and where each fails on catch-alls, disposables, and spam traps.
- [AI in Email Marketing: Between Hype and Reality](https://uchecker.net/blog-en/ai-email-marketing-2026): An honest look at AI in email marketing: what actually works, what is overhyped, and why list hygiene beats any generative model.
- [Email Validation Secrets: What Validators Won't Tell You](https://uchecker.net/blog-en/email-validation-secrets): Catch-all domains, greylisting, role-based addresses, disposable email — the non-obvious edge cases that make 100% accuracy impossible.
- [Corporate Email Server Components: MTA, MDA, MUA Explained](https://uchecker.net/blog-en/corporate-email-server-components): MTA, MDA, MUA, SMTP, IMAP, DNS records, TLS, anti-spam: every layer of a corporate mail server explained, with what breaks and why.
- [SPF, DKIM, and DMARC Explained: Email Authentication in Plain English](https://uchecker.net/blog-en/spf-dkim-dmarc-explained): Three DNS records that stop spoofing and protect your sender reputation. A practical walkthrough of SPF, DKIM, and DMARC — what they do, how they interact, and how to set them up in 30 minutes.
- [SPF, DKIM, and DMARC Setup: A Developer's Step-by-Step Guide](https://uchecker.net/blog-en/spf-dkim-dmarc-setup-guide): Configure SPF, DKIM, and DMARC via DNS with working record examples, common pitfalls, and tools to verify every step.
- [Email List Segmentation: A Beginner's Practical Guide](https://uchecker.net/blog-en/email-list-segmentation-guide): What email segmentation is, why it doubles CTR, and how to split your list into four working segments even if you're starting from scratch.
- [Advanced Email Segmentation: RFM Analysis, Behavior, and Lifecycle](https://uchecker.net/blog-en/email-segmentation-rfm-behavior-lifecycle): How to segment your list with RFM scoring, behavioral triggers, and lifecycle stages — with real conversion numbers from e-commerce, SaaS, and online schools.
- [Email Sender Reputation: What It Is and How to Check It](https://uchecker.net/blog-en/email-sender-reputation-explained): What sender reputation is, which factors control it, and five free tools you can use today to find out where your domain and IP actually stand.
- [How to Recover Your Email Sender Reputation](https://uchecker.net/blog-en/recover-email-sender-reputation): A step-by-step plan for recovering sender reputation after a blacklist hit: audit, list cleaning, delisting, IP warm-up, and ongoing monitoring.
- [Email Open Rate: What It Is and How to Improve It](https://uchecker.net/blog-en/email-open-rate-how-to-improve): What email open rate actually measures, what counts as good across industries, and 10 concrete ways to raise yours — including list hygiene, subject lines, and authentication.
- [Email Validation in Signup Forms: From Regex to API](https://uchecker.net/blog-en/email-validation-in-signup-forms): How to build real-time email validation into registration forms. JavaScript examples, error handling patterns, UX decisions, and when to call the API.
- [Hard Bounce vs Soft Bounce: Differences and What to Do](https://uchecker.net/blog-en/hard-bounce-vs-soft-bounce-explained): Learn what separates a hard bounce from a soft bounce, which SMTP codes signal each type, and the exact steps to handle both without damaging sender reputation.
- [Automated Bounce Handling: Webhooks, Logs, and Scripts](https://uchecker.net/blog-en/automated-bounce-email-processing): How to automate bounce processing: configure webhook endpoints, parse SMTP logs, and run suppression scripts to keep dead addresses out of your list.
- [Email Subject Line Formulas That Actually Get Opened: 15 Patterns](https://uchecker.net/blog-en/email-subject-line-formulas): 15 proven email subject line formulas with real examples. Covers A/B testing, length, emoji use, personalization, and why list hygiene matters first.
- [MX Records: What They Are and Why They Matter for Email Validation](https://uchecker.net/blog-en/mx-records-explained-email-validation): How MX records work in DNS, how to look them up with dig/nslookup, and their role in email validation — MX lookup, null MX, fallback, and common misconfigs.
- [Email Marketing for Online Stores: A Complete Guide](https://uchecker.net/blog-en/email-marketing-for-online-stores): Trigger flows, abandoned cart sequences, welcome series, post-purchase emails, and the metrics that actually matter for e-commerce revenue.
- [Email Sales Funnel: Setting Up Automated Drip Sequences](https://uchecker.net/blog-en/email-sales-funnel-drip-sequences): Build an email sales funnel that converts: welcome series, lead nurturing, conversion, and retention. Concrete email sequences with timings and triggers.
- [What Is Email Deliverability and What Affects It](https://uchecker.net/blog-en/what-is-email-deliverability): A plain-English breakdown of email deliverability: what inbox placement actually means, how it differs from delivery rate, and what moves the needle.
- [Email Deliverability Monitoring: Tools and Key Metrics](https://uchecker.net/blog-en/email-deliverability-monitoring-metrics): Which metrics to track for deliverability control, which tools to use, and how to build a dashboard that actually tells you what's happening.
- [Why Email Subscribers Unsubscribe and How to Stop It](https://uchecker.net/blog-en/why-email-subscribers-unsubscribe): The seven real reasons people unsubscribe from email lists — frequency, irrelevance, technical failures — and concrete fixes to lower your unsubscribe rate.
- [Email Regex Validation: Patterns From Naive to RFC 5322](https://uchecker.net/blog-en/regex-email-validation-patterns): A practical breakdown of email regex patterns in JavaScript, Python, and Go. Why regex alone isn't enough, and what to use alongside it for real validation.
- [Email Lead Magnets: 12 Formats That Actually Build Your List](https://uchecker.net/blog-en/email-lead-magnet-12-formats): Checklists, templates, calculators, mini-courses, quizzes — 12 lead magnet formats with real examples and conversion numbers. How to pick the right type, write the copy, and set up your opt-in form.
- [Double Opt-In vs Single Opt-In: Which Is Right for Your List](https://uchecker.net/blog-en/double-opt-in-vs-single-opt-in): Compare double opt-in and single opt-in by list quality, deliverability, signup conversion, and legal requirements. Data, real-world tradeoffs, and a clear decision guide.
- [Email Blacklists (DNSBL): How to Check and Get Delisted](https://uchecker.net/blog-en/email-blacklist-explained): What email blacklists are, why IPs and domains get listed, how to check your status across Spamhaus, Barracuda, and SpamCop, and what to do next.
- [Bulk Email Validation via API: Optimizing Large Lists](https://uchecker.net/blog-en/bulk-email-validation-api-large-lists): How to validate 100K+ addresses via API without timeouts or data loss. Batching, parallel polling, retry logic, and webhook notifications with Python and curl examples.
- [Email Personalization Beyond Merge Tags](https://uchecker.net/blog-en/email-personalization-beyond-merge-tags): How to move past first-name substitution: dynamic content blocks, behavioral triggers, product recommendations, and hyper-personalization for email marketing.
- [Python Email Validation: Libraries, Code Examples and Pitfalls](https://uchecker.net/blog-en/python-email-validation-libraries-and-pitfalls): Practical guide to email validation in Python: email-validator, dns.resolver, smtplib. Syntax, DNS and SMTP checks with working code examples.
- [Email Marketing Metrics: Benchmarks and What to Track](https://uchecker.net/blog-en/email-marketing-metrics-benchmarks): Open rate, CTR, CTOR, bounce rate, unsubscribe rate, and ROI — all key email marketing metrics with real industry benchmarks for 2025-2026.
- [A/B Testing Email Campaigns: What to Test and How to Analyze](https://uchecker.net/blog-en/ab-testing-email-campaigns): A practical guide to A/B testing email campaigns: choosing what to test, calculating sample size, reading results, and avoiding the mistakes that waste the data.
- [Email Design Best Practices and Trends for 2026](https://uchecker.net/blog-en/email-design-best-practices-2026): How to design emails people actually read: responsive layout, dark mode, accessibility, interactive elements, and minimalism. A practical guide with no filler.
- [Responsive HTML Email: Tables, CSS, and the Pitfalls](https://uchecker.net/blog-en/html-email-responsive-design): A practical guide to coding responsive HTML emails: table layouts, inline styles, media queries, Outlook compatibility, dark mode, and a pre-send checklist.
- [Email Domain and IP Warm-Up: A Complete 4-Week Guide](https://uchecker.net/blog-en/email-domain-ip-warmup-guide): Step-by-step domain and IP warm-up for email campaigns: a 4-week sending schedule, exact volume targets, key metrics to watch, and the mistakes that kill reputation fast.
- [How Email Providers Decide: Inbox or Spam?](https://uchecker.net/blog-en/how-email-providers-decide-spam-or-inbox): Four filtering layers, how Gmail, Mail.ru, and Yandex differ, and the steps that actually move the needle on inbox placement.
- [Email Marketing, Consent, and Personal Data: What You Need to Know](https://uchecker.net/blog-en/email-marketing-consent-and-personal-data): Every email address is personal data. Here's how consent requirements, data retention rules, fines, and list hygiene connect for email marketers.
- [GDPR and Email Marketing: EU Compliance Guide](https://uchecker.net/blog-en/gdpr-email-marketing-eu-compliance-guide): How to run email campaigns under GDPR: consent rules, double opt-in, right to erasure, data retention, and a practical checklist for marketers targeting EU audiences.
- [Email Copywriting That Gets Read All the Way Through](https://uchecker.net/blog-en/email-copywriting-that-gets-read): Structure, hooks, and before/after examples for email copy that holds attention from the first line to the CTA. Practical guide for email marketers.
- [AI Email Content Generation: Tools, Prompts, and Real Limits](https://uchecker.net/blog-en/ai-email-content-generation-tools-and-prompts): How to use ChatGPT, Claude, and specialized platforms for email campaigns: prompts that actually work, editing AI drafts, and honest limitations.
- [What Is an Email API and Why Your Business Needs One](https://uchecker.net/blog-en/what-is-email-api): Plain-English explanation of email APIs: how they work, what types exist, when you need one, and how real-time validation protects your sender reputation.
- [Email Event Webhooks: Setup, Handling, and Debugging](https://uchecker.net/blog-en/email-webhook-setup-and-handling): How to receive, verify, and process email webhooks from SendGrid, Mailgun, and Amazon SES. HMAC signatures, idempotency, queue patterns, and Node.js examples.
- [Triggered Email Campaigns: 12 Types With Examples](https://uchecker.net/blog-en/triggered-email-campaigns-types-and-examples): A practical breakdown of 12 triggered email types — welcome, abandoned cart, reactivation, and more — with subject line examples and send logic for each.
- [Transactional vs Marketing Email: Differences and Rules](https://uchecker.net/blog-en/transactional-vs-marketing-email): How transactional and marketing emails differ, what legal requirements apply to each, and how mixing them on the same infrastructure destroys deliverability.
- [How to Clean Your Email List After a Long Sending Gap](https://uchecker.net/blog-en/clean-email-list-after-long-pause): Step-by-step plan for cleaning an email list that has been idle for 6+ months: validation, removing dead addresses, segmentation, and a safe restart.
- [Email Subscriber Churn Prediction: Models and Real-World Practice](https://uchecker.net/blog-en/email-subscriber-churn-prediction): How ML models predict email subscriber churn: input features, algorithms, quality metrics, and how to act on predictions before subscribers are gone.
- [Best Time to Send Email Campaigns: Data and Tests](https://uchecker.net/blog-en/best-time-to-send-email-campaigns): When should you send email campaigns for the highest open rates? We break down research from GetResponse, Mailchimp, and Omnisend, and explain how to run your own time tests.
- [How AI Picks the Best Send Time for Each Subscriber](https://uchecker.net/blog-en/send-time-optimization-ai-algorithms): A technical breakdown of send time optimization: event pipeline, three modeling approaches, cold-start strategies, and the traps that break STO in production.
- [SaaS Email Marketing: Strategy, Sequences and Metrics](https://uchecker.net/blog-en/saas-email-marketing-strategy-sequences-metrics): How to build an email program that moves SaaS users from signup to paid: onboarding sequences, trial-to-paid conversion, churn prevention, and the metrics that matter.
- [Email Validation in CRM: Bitrix24, amoCRM, and HubSpot Integration](https://uchecker.net/blog-en/email-validation-crm-integration-bitrix24-amocrm-hubspot): How to integrate email validation into Bitrix24, amoCRM, and HubSpot. Working code examples in PHP, Python, and Node.js. Webhook setup, bulk cleanup, and automated workflows.
- [How to Keep Emails Out of Gmail's Promotions Tab](https://uchecker.net/blog-en/gmail-promotions-tab-avoid-primary-inbox): Why Gmail routes emails to Promotions, which signals trigger it, and eight concrete steps to land in the Primary inbox instead.
- [Google Postmaster Tools and Yahoo Sender Hub: Setup and Reports](https://uchecker.net/blog-en/google-postmaster-tools-setup-and-reports): How to set up Google Postmaster Tools and Yahoo Sender Hub, read domain reputation reports, interpret spam rate data, and act on delivery errors.
- [B2B Email Marketing: Strategy, Segmentation, Lead Nurturing](https://uchecker.net/blog-en/b2b-email-marketing-strategy-lead-nurturing-segmentation): How B2B email differs from B2C: long sales cycles, buying committees, role-based segmentation, and nurturing sequences that build trust before pitching.
- [Node.js Email Validation: Libraries, Services, Best Practices](https://uchecker.net/blog-en/nodejs-email-validation-libraries-and-services): Compare email-validator, deep-email-validator, Zod, and external APIs for Node.js. Code examples for middleware, MX checks, bulk validation, and caching.
- [How to Choose an Email Service Provider in 2026](https://uchecker.net/blog-en/how-to-choose-an-email-service-provider-2026): Comparing Unisender, Sendsay, Mailchimp, and Brevo across 7 criteria: pricing model, automation depth, deliverability, and data residency. Concrete pros and cons, no filler.
- [AI Real-Time Email Personalization: Architecture and Implementation](https://uchecker.net/blog-en/ai-real-time-email-personalization): How ML-driven email personalization actually works: feature stores, recommendation models, dynamic rendering pipelines, and where list quality fits in.
- [Email Accessibility: How to Make Your Campaigns Readable for Everyone](https://uchecker.net/blog-en/email-accessibility-best-practices): Alt text, contrast ratios, semantic markup, screen reader compatibility, font sizes, and button targets — a practical guide to accessible email design.
- [IP Reputation vs Domain Reputation: What Matters More in 2026](https://uchecker.net/blog-en/ip-reputation-vs-domain-reputation): IP reputation and domain reputation work at different layers of email delivery. Learn which one carries more weight in 2026, how to check both, and where to focus.
- [A Subscriber Marked You as Spam: How to Get Back to the Inbox](https://uchecker.net/blog-en/spam-complaint-recovery-back-to-inbox): What happens when a subscriber hits the Spam button, how FBL feedback loops work, and a step-by-step plan for recovering inbox placement.
- [Email Validation at the Infrastructure Level: Milter and Postfix](https://uchecker.net/blog-en/email-validation-milter-postfix-infrastructure): How to validate email at the MTA layer using Postfix restriction classes, policy servers, and milter filters — with configuration examples and architecture breakdown.
- [10 Email Marketing Mistakes That Kill Deliverability](https://uchecker.net/blog-en/email-marketing-mistakes-that-kill-deliverability): Ten concrete mistakes that send your emails to spam, each with a specific fix. For anyone tired of guessing why open rates keep dropping.
- [How Spam Filters Work: AI and Machine Learning Explained](https://uchecker.net/blog-en/how-spam-filters-work-ai-and-machine-learning): How Gmail, Outlook, and Mail.ru separate campaigns from spam — Bayesian filters, neural networks, behavioral signals, and what every email marketer needs to know.
- [Email Marketing Trends 2026: What's Actually Working Now](https://uchecker.net/blog-en/email-marketing-trends-2026): Interactive emails, AMP, AI personalization, zero-party data, and list hygiene: the 2026 email trends that move real numbers, with concrete data and no hype.
- [BIMI Record Setup: Add Your Logo to Email Inboxes](https://uchecker.net/blog-en/bimi-record-setup-guide): Step-by-step guide to configuring BIMI: DNS TXT record, SVG Tiny PS logo requirements, VMC certificate, and DMARC prerequisites. Includes dig commands and common pitfalls.
- [Email List from Scratch: A Step-by-Step Plan to Your First 1,000 Subscribers](https://uchecker.net/blog-en/email-list-from-scratch-first-1000-subscribers): A practical step-by-step plan for building your first 1,000 email subscribers. Opt-in forms, lead magnets, content strategy, social channels, and list validation at every stage.
- [Email Analytics Data Pipeline: From Webhook to Dashboard](https://uchecker.net/blog-en/email-analytics-data-pipeline): How to build an email analytics pipeline: webhook receiver, message queue, ETL enrichment, ClickHouse storage, and Grafana dashboards. With code examples.
- [Welcome Email Best Practices and Sequence Examples](https://uchecker.net/blog-en/welcome-email-best-practices): How to write a welcome email people actually open and read. Structure, timing, 3-5 email sequence examples, and the mistakes that kill conversion in the first week.
- [DKIM Key Rotation: Why, When, and How to Do It Right](https://uchecker.net/blog-en/dkim-key-rotation): A practical guide to rotating DKIM keys: generate new keys, switch selectors without downtime, and automate via cron or CI/CD.
- [Abandoned Cart Emails: Recovery Strategies That Work](https://uchecker.net/blog-en/abandoned-cart-email-recovery-strategies): A practical guide to abandoned cart email sequences: timing, content, segmentation, email validation, and the metrics that tell you if it's actually working.
- [SPF flattening: how to work around the 10 DNS lookup limit](https://uchecker.net/blog-en/spf-flattening-10-dns-lookup-limit): What SPF flattening is, why you need it, and how to implement it manually or with a service. Record examples, automation scripts, and real pitfalls.
- [Post-Purchase Email Sequence: 6 Emails That Drive Repeat Sales](https://uchecker.net/blog-en/post-purchase-email-sequence): Order confirmation to replenishment: timings, metrics, and content for every stage of a post-purchase email series that actually converts.
- [Apple Mail Privacy Protection: What It Does to Email Marketing](https://uchecker.net/blog-en/apple-mail-privacy-protection-mpp-email-marketing): MPP pre-fetches tracking pixels before anyone reads your email. Here's what breaks, what still works, and how to adapt your analytics in 2026.
- [Loyalty Program Email Strategy: Tiers, Triggers, and List Hygiene](https://uchecker.net/blog-en/loyalty-program-email-strategy): How to build a loyalty program email channel: tier-based segmentation, seven trigger sequences, frequency caps, and list hygiene that keeps deliverability intact.
- [Gmail Sender Requirements in 2026: What Actually Changed](https://uchecker.net/blog-en/gmail-sender-requirements-2026): SPF, DKIM, DMARC, one-click unsubscribe, complaint thresholds, bounce handling — what Gmail now enforces for bulk senders and how to stay compliant.
- [How to Build a Newsletter People Actually Read](https://uchecker.net/blog-en/newsletter-strategy-and-format): Strategy, format, and frequency for newsletters: how to turn a recurring email into something subscribers genuinely look forward to opening.
- [Yahoo Sender Requirements 2026: What You Must Comply With](https://uchecker.net/blog-en/yahoo-sender-requirements-2026): Yahoo requires SPF, DKIM, DMARC at p=quarantine, one-click unsubscribe, TLS 1.2+, and a complaint rate below 0.3%. Here is what changed and how to comply.
- [Email Marketing for Webinars and Events: The Full Cycle](https://uchecker.net/blog-en/email-marketing-for-webinars-and-events): How to run email sequences for webinars and live events: invitation chains, reminders, post-event follow-up, list segmentation, and what to do with registrant data.
- [Mail.ru Email Deliverability: What You Need to Know](https://uchecker.net/blog-en/mail-ru-email-deliverability-guide): How Mail.ru filters email, what makes it different from Gmail, and what to do to land in the inbox on Russia's largest mail provider.
- [Win-Back Email Campaign: How to Recover Lost Customers](https://uchecker.net/blog-en/win-back-email-campaign-recover-lost-customers): Build a win-back email sequence that converts: segment lapsed customers, time each send, write subject lines that get opened, and validate your list first.
- [Yandex Mail Deliverability: Setup Guide for Senders](https://uchecker.net/blog-en/yandex-mail-deliverability-guide): How Yandex.Mail filters email, which DNS records it actually enforces, how Yandex Postmaster works, and what to do when campaigns land in spam on yandex.ru.
- [Birthday and Anniversary Email Automation That Converts](https://uchecker.net/blog-en/birthday-anniversary-email-automation): How to build birthday and anniversary email sequences: collecting dates, three-email timing, offer types, technical setup, and metrics to track.
- [Custom Tracking Domain: Why It Matters and How to Set It Up](https://uchecker.net/blog-en/custom-tracking-domain-setup): Step-by-step guide to setting up a custom tracking domain for email campaigns: CNAME records, DNS configuration, SSL, and deliverability impact.
- [Email Referral Program: How to Launch One That Works](https://uchecker.net/blog-en/email-referral-program): How to run a referral program through email: mechanics, email sequences, rewards, tracking, and common mistakes. A practical guide with real numbers.
- [Email Header Analysis: How to Read and Diagnose Problems](https://uchecker.net/blog-en/email-header-analysis-guide): A practical guide to reading email headers: from the Received chain to Authentication-Results. Real header examples, common failure patterns, and step-by-step diagnosis.
- [Email + SMS: Integrating Channels for Maximum Reach](https://uchecker.net/blog-en/email-sms-integration-omnichannel-campaigns): A practical guide to email and SMS integration: architecture, timing, consent rules, data quality, and the metrics that prove whether the combo actually works.
- [How to Spot a Phishing Email: A Technical Breakdown](https://uchecker.net/blog-en/how-to-spot-a-phishing-email): Anatomy of phishing emails at the header, DNS, and content level. Concrete signals, verification tools, and why list hygiene keeps your domain out of the spam bucket.
- [Email Preference Center: Give Subscribers Real Control](https://uchecker.net/blog-en/email-preference-center-guide): What an email preference center is, what belongs on the page, how to wire it to your ESP, and four metrics to track after launch. Practical guide.
- [Email List Decay: How Fast Your Database Goes Stale](https://uchecker.net/blog-en/email-list-decay-rate): B2B lists lose 22–30% of valid addresses per year. Here's the data on how decay compounds, what drives it faster, and how often you actually need to revalidate.
- [Email Content Calendar: Plan a Month of Campaigns](https://uchecker.net/blog-en/email-content-calendar-planning): How to build an email content calendar: structure, sending frequency, content mix, seasonal timing, and the mistakes that kill consistency.
- [Email Rendering Across Clients: Testing and Compatibility](https://uchecker.net/blog-en/email-rendering-across-clients): Why the same email looks broken in Outlook, clipped in Gmail, or invisible in dark mode — and what to test before you hit send.
- [Re-Permission Campaign: How to Ask for Consent Again](https://uchecker.net/blog-en/re-permission-campaign-recollect-consent): When and why to run a re-permission campaign, how to write the email, what results to expect, and why validating your list beforehand is non-negotiable.
- [MTA-STS Setup: Stop Email TLS Downgrade Attacks](https://uchecker.net/blog-en/mta-sts-setup-guide): Step-by-step guide to deploying MTA-STS (RFC 8461): policy file, Nginx config, DNS TXT record, TLS-RPT reporting, and a full validation script.
- [Email Sunset Policy: When and How to Remove Inactive Subscribers](https://uchecker.net/blog-en/email-sunset-policy-inactive-subscribers): A sunset policy removes disengaged subscribers before they drag down deliverability. Learn how to set thresholds, run re-engagement sequences, and automate the process.
- [Email Client Market Share in 2026: What the Data Means for Your Templates](https://uchecker.net/blog-en/email-client-market-share-2026): Apple Mail holds 52-58% of opens, Gmail sits at 27-30%, and Outlook still renders with Word. Here's what email client market share data means for your HTML templates.
- [Product Launch Email Campaign: A Step-by-Step Plan](https://uchecker.net/blog-en/product-launch-email-campaign): Build a product launch email campaign that converts: three-phase structure, per-email timing, subject lines, metrics to track, and list hygiene before you hit send.
- [Mobile Email Optimization: What to Fix Before You Send](https://uchecker.net/blog-en/mobile-email-optimization): A practical guide to mobile email optimization: single-column layout, touch targets, font sizes, image weight, preheader copy, and real-device testing.
- [Seasonal Email Campaigns: Black Friday, New Year, and Beyond](https://uchecker.net/blog-en/seasonal-email-campaigns): How to prepare email campaigns for seasonal peaks: Black Friday, New Year, Women's Day. Timeline, segmentation, list hygiene, and sequence examples.
- [Gmail Annotations: Promo Cards and Product Carousels](https://uchecker.net/blog-en/gmail-promotions-annotations-schema): How to implement Gmail Annotations with schema.org markup: promo cards, product carousels, deal badges, image specs, common failures, and ESP compatibility.
- [Email Storytelling: How to Write Emails People Actually Finish](https://uchecker.net/blog-en/email-storytelling-techniques): Practical storytelling techniques for email campaigns: mini-story structure, open loops, failure arcs, and the deliverability baseline that makes all of it matter.
- [Email Testing Tools: Litmus, Email on Acid, and Alternatives](https://uchecker.net/blog-en/email-testing-tools-litmus-email-on-acid): Litmus vs Email on Acid vs Mailtrap: rendering previews, dark mode, spam scoring, pricing. How to pick the right pre-send testing tool for your workflow.
- [Email Marketing for Marketplace Sellers](https://uchecker.net/blog-en/email-marketing-for-marketplace-sellers): How marketplace sellers can build an owned email channel: collecting subscribers without platform data, writing sequences that drive repeat orders, and keeping deliverability clean.
- [How Email Forwarding Breaks SPF, DKIM, and DMARC](https://uchecker.net/blog-en/email-forwarding-authentication-failure): Why server-side forwarding causes SPF failures, when DKIM breaks, how ARC preserves authentication state across hops, and what senders can do about it.
- [Video in Email: How to Use It Without Killing Deliverability](https://uchecker.net/blog-en/video-in-email-deliverability): How to add video to email campaigns without landing in spam. Practical methods: GIF previews, static thumbnails, HTML5 video, email client limits, and real deliverability impact.
- [How Email Open and Click Tracking Actually Works](https://uchecker.net/blog-en/email-open-click-tracking-how-it-works): Tracking pixels, redirect chains, HTTP headers: how open and click tracking work in email, what corrupts the data, and what you can actually trust.
- [Email Surveys and Feedback Collection: Formats That Work](https://uchecker.net/blog-en/email-survey-feedback-guide): How to collect feedback via email: survey formats, embedded ratings, NPS, open questions. Practical tactics that lift response rates and produce usable data.
- [Automating Email Hygiene via API: Architecture and Code](https://uchecker.net/blog-en/email-hygiene-automation-api): Build an automated email list cleaning pipeline using a validation API: Python and Node.js examples, batch submission, polling, cron scheduling, and database updates.
- [Plain Text vs HTML Email: When to Use Each Format](https://uchecker.net/blog-en/plain-text-vs-html-email): Deliverability, reply rates, and real use cases for plain text vs HTML email. A practical framework for choosing the right format instead of defaulting to your ESP.
- [SMTP Relay Services Compared: SendGrid, Amazon SES, Mailgun](https://uchecker.net/blog-en/smtp-relay-services-comparison): Detailed comparison of SendGrid, Amazon SES, and Mailgun: pricing, deliverability, API quality, dedicated IPs, and where each service trips you up.
- [How to Calculate Email Marketing ROI: Formulas and Examples](https://uchecker.net/blog-en/email-marketing-roi-calculation): The real ROI formula for email campaigns — what costs to include, which attribution model to use, and where teams consistently get the math wrong.
- [Email Compliance Audit: How to Check Your Campaigns](https://uchecker.net/blog-en/email-compliance-audit-checklist): A practical guide to auditing email campaigns for CAN-SPAM, GDPR, and industry standards: consent records, SPF/DKIM/DMARC, unsubscribe mechanics, and data retention.
- [Email Gamification: Interactive Mechanics That Lift Engagement](https://uchecker.net/blog-en/email-gamification-mechanics): Scratch cards, quizzes, progress bars, countdown timers — how each mechanic works inside the inbox, what to watch out for, and why list hygiene comes first.
- [Email in Dark Mode: How to Design Without Breaking It](https://uchecker.net/blog-en/email-dark-mode-design): A practical guide to dark mode email design: how Gmail, Apple Mail, and Outlook invert colors differently, what breaks, and how to fix each case.
- [Email Customer Journey Map: Match Every Send to Its Stage](https://uchecker.net/blog-en/email-customer-journey-map): Build a customer journey map for email: identify touchpoints, set behavioral triggers, assign the right message type at each stage, and keep your list clean.
- [Email Encryption: S/MIME vs. PGP and When You Actually Need It](https://uchecker.net/blog-en/email-encryption-smime-pgp): A practical comparison of S/MIME and PGP: trust models, key management, client support, and the real-world scenarios where email encryption is worth the setup cost.
- [Email Marketing for Restaurants and Cafes: A Practical Guide](https://uchecker.net/blog-en/restaurant-email-marketing-guide): How food service businesses can build a guest list, set up automated sequences, run seasonal campaigns, and protect deliverability — without wasting ad budget.
- [Pre-Send Email QA Checklist: 20 Checks Before You Send](https://uchecker.net/blog-en/pre-send-email-qa-checklist): 20 pre-send checks covering subject line, SPF/DKIM/DMARC, list validation, mobile rendering, and more. A practical checklist for every email team.
- [Multilingual Email Campaigns: Localization Done Right](https://uchecker.net/blog-en/multilingual-email-campaigns-localization): How to build multilingual email campaigns that convert: template architecture, language detection, translation workflows, regional compliance, and list validation per segment.
- [AI Subject Line Optimization: Tools and How to Use Them](https://uchecker.net/blog-en/ai-subject-line-tools): A practical guide to AI subject line tools: Phrasee, Jasper, ESP built-ins, bandit testing, and why list hygiene sets the ceiling on open rate gains.
- [GIF in Email: File Size, Optimization, and Client Support](https://uchecker.net/blog-en/gif-in-email-optimization-guide): How to use animated GIFs in email campaigns: file-size targets, frame-rate optimization, client support matrix, Outlook fallbacks, and accessibility rules.
- [AI Tools for Automatic Email List Segmentation](https://uchecker.net/blog-en/ai-email-segmentation-tools): How AI segmentation tools work, what platforms actually deliver in production, and why list hygiene is the prerequisite that every predictive model depends on.
- [Email Footer Best Practices: What to Include and How to Do It](https://uchecker.net/blog-en/email-footer-best-practices): Everything that belongs in an email footer: unsubscribe link, physical address, legal disclosures (CAN-SPAM, GDPR, CASL), preference center, and design rules.
- [Predictive Email Send Optimization: Beyond STO](https://uchecker.net/blog-en/predictive-send-optimization-beyond-sto): What lies beyond Send Time Optimization: multi-factor models, dynamic frequency caps, subscriber fatigue prediction, and the architecture of a predictive send pipeline.
- [Email CTA Button: Design, Copy, and Placement](https://uchecker.net/blog-en/email-cta-button-design): How to design an email CTA button that actually gets clicked: size, colour, copy, placement, and the five mistakes that quietly kill your click-through rate.
- [AI for Email Content Testing: Automated Pre-Send QA](https://uchecker.net/blog-en/ai-email-pre-send-qa-automation): How AI catches broken links, spam filter triggers, rendering failures, and tone issues before your campaign reaches subscribers. A practical pre-send QA guide.
- [Real Estate Email Marketing: Strategy and Automation](https://uchecker.net/blog-en/real-estate-email-marketing-strategy): How real estate agencies and developers use email: segment by deal type, build buyer and renter sequences, and nurture long decision cycles without burning ad budget.
- [Email Deliverability Checklist for a New Domain](https://uchecker.net/blog-en/email-deliverability-checklist-new-domain): 12-step checklist to prepare a new domain for email sending: DNS records, SPF/DKIM/DMARC, list validation, warmup schedule, and common mistakes to avoid.
- [Email Marketing for Financial Services: Compliance and Conversion](https://uchecker.net/blog-en/email-marketing-for-financial-services): How to run email campaigns in the financial sector: regulatory requirements, segmentation, drip sequences, and list hygiene. Practical, no filler.
- [TLS-RPT: Monitor Email Encryption Between Mail Servers](https://uchecker.net/blog-en/tls-rpt-setup-and-monitoring): Set up TLS-RPT in one DNS record, read the JSON reports, fix certificate errors, and combine it with MTA-STS for enforced TLS on your domain.
- [Email Marketing for Online Courses and Edtech](https://uchecker.net/blog-en/email-marketing-for-online-courses-edtech): How edtech projects build an email channel that works: onboarding sequences, dropout recovery, lead nurturing, list hygiene, and metrics that matter.
- [DANE for Email: How to Set Up DNS-Based TLS Authentication](https://uchecker.net/blog-en/dane-email-tlsa-setup): A practical guide to DANE for mail servers: TLSA records, generating certificate hashes, verifying with dig, DNSSEC dependency, and how it compares to MTA-STS.
- [Healthcare Email Marketing: HIPAA, Ethics, and Automation](https://uchecker.net/blog-en/healthcare-email-marketing-hipaa-compliance): How clinics and medical practices build compliant patient email programs: HIPAA rules, ethical limits, appointment reminder sequences, and list hygiene.
- [Email Marketing Benchmarks by Industry: 2026 Data](https://uchecker.net/blog-en/email-marketing-benchmarks-by-industry-2026): Open rate, CTR, bounce rate, and unsubscribe rate benchmarks for 12 industries in 2026. Tables, variance analysis, and practical takeaways.
- [Email Marketing for Nonprofits and Charities](https://uchecker.net/blog-en/nonprofit-email-marketing-strategy): How nonprofits can build a reliable email channel: donor list growth, thank-you sequences, engagement segmentation, and address validation for high deliverability.
- [How to Keep Deliverability Intact When Switching ESPs](https://uchecker.net/blog-en/esp-migration-email-deliverability): A step-by-step playbook for migrating to a new email service provider without inbox placement drops: DNS setup, IP warmup, traffic phasing, and monitoring.
- [Hotel Email Marketing: Direct Bookings and Guest Loyalty](https://uchecker.net/blog-en/hotel-email-marketing-direct-bookings-loyalty): How hotels and travel agencies use email to drive direct bookings, bring guests back, and build loyalty without paying 15-25% OTA commissions.
- [Null MX: Protect Domains That Don't Accept Email](https://uchecker.net/blog-en/null-mx-record-domain-protection): How RFC 7505 Null MX works, why every non-mail domain needs it, and how to set up MX 0 . alongside SPF -all and DMARC p=reject in under five minutes.
- [Email Marketing for Mobile Apps: Onboarding and Retention](https://uchecker.net/blog-en/mobile-app-email-onboarding-retention): How to build an email strategy for your mobile app: onboarding sequences, deep links, push vs email orchestration, retention triggers, and list hygiene.
- [Reverse DNS and Email: PTR Records and FCrDNS Explained](https://uchecker.net/blog-en/reverse-dns-ptr-record-fcrdns-email): What a PTR record is, how reverse DNS (rDNS) works, and what FCrDNS checks. Configure PTR for your mail server, diagnose with dig, and understand the deliverability impact.

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