Email Open Rate: What It Is and How to Improve It

Your campaign report says 23% of recipients opened the email. How much that tells you depends on how the number was calculated, which mail apps your subscribers use, and how many addresses on the list belong to inboxes nobody checks anymore. And since 2021 a share of those “opens” haven’t come from people at all.

What open rate is and how it’s calculated

Open rate is the share of delivered emails that recipients opened. Take unique opens, divide by delivered messages, multiply by 100. Ten thousand delivered and 2,300 opened gives you 23%.

The base is delivered mail, not sent mail. If 500 of 10,000 emails bounced, the denominator is 9,500. Opens are counted once per person, so a subscriber who opens the same email five times still counts as one. Most reports show total opens next to unique opens, and open rate uses the unique figure.

How an open gets recorded

Your sending platform puts a tracking pixel into the HTML version of the email: a transparent 1×1 image whose URL is unique to the recipient and the campaign. When the mail app loads images, that request reaches the sender’s server and an open is logged.

The method misses in both directions. No open is recorded when someone has image loading turned off, reads in plain text, or sits behind a corporate filter that strips external images. A false open shows up when an antivirus tool or a receiving server fetches the images to scan them before the person has seen anything.

Apple Mail Privacy Protection and why the number is inflated

Mail Privacy Protection (MPP) arrived with iOS 15 on September 20, 2021. In Apple’s short description, it hides the recipient’s IP address and stops senders from seeing whether a message was opened. The mechanics are explained on Apple’s privacy page: when a message arrives in Mail, remote content, including the tracking pixel, is downloaded in the background through Apple’s relays, whether or not the person ever looks at the email.

To the sender, that background download looks exactly like an open. Apple notes that the protection doesn’t extend to links or attachments, so clicks remain real. MPP is a setting in Mail, and not everyone has it on, which means the share of machine opens varies from list to list. By opens, a consumer list full of iPhone owners will look far healthier than a B2B list that lives in Outlook.

What counts as a good open rate

There isn’t a universal benchmark. Email platforms publish industry averages, but each one calculates them from its own customers with its own rules, and since MPP those averages include machine opens too. A market average says little about your list.

I’d compare a campaign with its own history instead: the same type of email, the same audience, several months in a row. A steady rate that suddenly drops points to a problem with delivery, the list, or the subject lines. A rate that climbs while you changed nothing? Check whether the share of Apple Mail users on the list has grown, because that kind of growth tells you nothing about interest.

Why open rates drop

Before trying to raise the number, find out what’s pulling it down. These five causes come up most often.

1. Dead and abandoned addresses. A mailbox that doesn’t exist bounces and drops out of the open rate math, but bounces still damage your sender reputation. Abandoned inboxes that still accept mail are worse. The message counts as delivered and nobody is there to open it. People change jobs, start new accounts, forget passwords, and a list ages without any help from you.

2. Forgettable subject lines. Subject, sender name and preheader are all a recipient sees before deciding. If the subject looks like everything else in the inbox, it gets skipped. “Company news for March” reads like permission to scroll past.

3. No preheader. The preheader (preview text) is the line shown right after the subject in Gmail, Outlook and most other inboxes. Leave it empty and the mail app grabs the first words of the body instead, which usually means “View in browser” or “Hi {name}”.

4. Bad send time. An email sent at 3 a.m. is buried under a dozen others by morning, and a Friday evening send competes with the weekend. The right hour differs from one audience to the next.

5. Mail lands in spam. Almost nobody opens the spam folder, so the rate falls on its own. Missing SPF, DKIM or DMARC? A new domain that was never warmed up? A history of complaints? Any one of these keeps mail out of the inbox. The deliverability guide covers each of them.

10 ways to raise open rate

Start with the list and the domain, since they decide whether the email reaches the inbox at all, and the subject only does its work once it’s there.

1. Clean the list. Invalid addresses bounce, and bounces hurt reputation. Spam traps, abandoned inboxes and catch-all domains, which accept mail for any address, behave differently. The email is delivered, nobody reads it, and the open rate sinks. Run the list through a validator and remove the invalid addresses. Keep the unknown ones out of your first large send.

2. Write subjects like a note to a friend. Skip “Monthly digest #47.” You want one reaction, “I should open this.” Specific numbers, questions and unexpected angles tend to work. Compare “Email marketing tips” with “Why 8% of your subscribers open your emails (and what to do about it)”. Only the second gives a reason to open. Long subjects get cut off, sooner on a phone than on a desktop, so put the important words first. And don’t fake a conversation. Google explicitly asks senders not to start subjects with Re: or Fwd: unless the message really is a reply or a forward.

3. Treat the preheader as the second half of the subject. The subject hooks, the preheader closes. Subject “3 mistakes that kill deliverability,” preheader “The third one is the least obvious.” Together they take up two lines in the inbox. Most platforms let you set the preheader separately from the body.

4. Test send times. Freelancers read mail in the evening, accountants first thing Monday, parents of small kids at 11 p.m. once the house is quiet. Send the same email to different parts of the list at different times, and repeat over several campaigns. Judge the result by clicks, because Apple’s machine opens fire at delivery time, whenever the person actually reads.

5. Sign the email as a person. “Maria from uChecker” is easier to recognize than “uChecker Inc.”, and a faceless noreply@ loses to both. If a real person runs the newsletter, use their name. Google also notes that messages from an address in the recipient’s contacts are less likely to be marked as spam, so a stable sender address helps delivery too.

6. Segment the list. One email to everyone gets you an average result. Split subscribers into at least two groups, active and everyone else. Mail the active group regularly and the dormant one less often, with only your best content. The segmentation guide goes further.

7. A/B test subject lines. Take a small slice of the list, split it in half and send two subject variants at the same time. A few hours later, check which got more opens and send the winner to everyone else. Most platforms automate this, and open rate still works honestly here: machine opens land in both halves at roughly the same rate, as long as the halves come from the same list and go out together.

8. Authenticate your domain. SPF, DKIM and DMARC are DNS records that let the receiving server confirm the email really came from you. Since February 1, 2024, Gmail has required SPF or DKIM from every sender, and SPF, DKIM and DMARC together from anyone sending more than 5,000 messages a day to Gmail accounts (a DMARC policy of none is enough). Without them, part of your mail never reaches the inbox and the open rate suffers for reasons that have nothing to do with the subject. Setup steps are in the SPF, DKIM and DMARC guide.

9. Remove inactive subscribers. Google suggests considering unsubscribing people who don’t open or read your messages. Yahoo warns that mailing people who aren’t reading harms your reputation and recommends sending inactive subscribers a reconfirmation email from time to time. Hard to let go of contacts you worked for, sure. Run a reactivation sequence first and decide after; the reactivation guide shows how to build one.

10. Keep a steady schedule. Subscribers get used to a rhythm. Send weekly for three months, go silent for six weeks, then drop a promo, and opens will be low because people forgot who you are. Some will hit “Report spam.” Pick a frequency you can actually keep up and stay with it.

Open rate and deliverability

Mailbox providers don’t publish how they weigh recipient behavior. They do say openly that engagement and delivery are linked. Yahoo puts it plainly: the best way to get delivered is to send timely, relevant email to an active, engaged audience. Google notes that letting people opt out easily can improve open rates, click-through rates and sending efficiency.

So the loop runs like this. Unread email drags reputation down, a weaker reputation puts less mail in the inbox, and opens fall further. You can break it from either side, by removing addresses that will never open, or by giving the people who do receive your email a reason to open it.

What to measure instead of opens

Clicks survived MPP because a click takes a human, although some corporate filters follow links before the recipient does. Conversions are more honest still, meaning the purchase, signup or whatever else the email asked for. Replies are a good signal too, especially in B2B.

For list cleaning, a single open in a single campaign means little. Look at activity over a long window instead, for example whether an address clicked anything in recent months. Open rate itself is still useful for comparing two subject lines in an A/B test, where the inflation hits both halves equally.

Checklist for this week

• Run the list through a validator. Remove invalid addresses and set the unknown ones aside.
• Confirm SPF, DKIM and DMARC are configured for your sending domain.
• Create two segments: active (clicked in recent months) and everyone else.
• Rewrite the subject of your next send with something specific: a number, a question or a clear benefit.
• Fill in the preheader by hand. It should extend the subject, not repeat it.
• Run a subject line A/B test on a small slice of the list and send the winner to the rest.