Check if an email
address exists
We ask the mail server whether the mailbox is there and show you its reply word for word. No email is sent and no signup is needed.
What happens during a check
Five stages, all of them visible in the report. If an address fails early, the check stops there.
- Address format
Stray spaces, invisible characters picked up from the clipboard, a Cyrillic letter hiding in a Latin address. The address is checked exactly as you typed it, never corrected.
- Domain and MX
Does the domain exist, and who receives its mail? You get the MX hosts in order, plus the provider's name when we recognise it.
- Connection
We connect to port 25 and turn on encryption if the server offers it. The report names the server, the TLS version and the sending host we used.
- Control address
First we ask about an address that cannot exist. If the server accepts that one, its yes means nothing for the real mailbox and the verdict stays unknown.
- Your mailbox
We ask with RCPT TO and hang up before any message is transferred. The reply goes into the report as it came, down to a line like 550 5.1.1 User unknown.
We don't guess. When a server won't say, the report says so.
The three answers
goodMailbox exists
The server accepted the address and refused a made-up one on the same domain. Nothing less earns a green result.
badNowhere to send
An explicit refusal, a full mailbox, or a domain with no mail server. Take this address off your list.
unknownUnknown
Catch-all, a silent server, a refusal to confirm, a blocklist hit on our side. The address may be fine, but nothing proves it.
What a check can't tell you
- Whether anyone reads that inbox.
A server answers the same way for an abandoned mailbox as for a busy one, until the account is closed.
- Whether your email lands in the inbox.
That depends on your own domain and its reputation. You can test your domain setup separately.
- What happens after acceptance.
Some servers agree to everything during the conversation and send the bounce later as a separate message.
FAQ
Will the person know I checked their address?
No. The conversation ends at the recipient question and never reaches the DATA command, so no message exists and nothing arrives in their inbox.
Why only five checks a day?
Every check is a live connection to someone else's mail server. Ask too often and our sending addresses get blocked, which would end the tool for everyone. That's the reason for the captcha, the limit per IP and the pause we keep between visits to the same server.
Why do I sometimes have to wait?
Some servers tell an unfamiliar sender to come back later and name the delay themselves. This is greylisting, and we never return before the time they named. If the wait is too long for a page, you get the server's reply and an unknown verdict.
What does a server that accepts everything mean?
The domain may be set up to receive mail for any address, known as catch-all, or the server simply doesn't tell recipients apart at this stage. Either way its yes proves nothing, so the verdict is unknown.
Why is my Mail.ru address not checked?
The Mail.ru group doesn't answer these questions over SMTP, so this page returns unknown rather than a guess. Your dashboard has a separate check for those mailboxes.
What happens to the address I enter?
The address is only needed for the check and never goes into a mailing list. For the limit we count requests from your IP.
Can I check a whole list?
Yes, in the dashboard or through the API. A single job takes up to 9 million addresses, the first 100 are free, and signup doesn't ask for a card.
Got an address you're not sure about?
Five free checks a day, with the server's full reply.
Check addressNeed to check a list? The first 100 addresses in the dashboard are free