If your email open rates have dropped and you're not sure why, you're not alone. It's one of the most common questions UK marketing teams search for, and the answer is rarely simple.
The frustrating part is that a drop in open rates can mean several different things. Some of them are serious. Some of them are not. And one of the most significant causes in recent years has nothing to do with your emails at all.
This post walks through the real reasons open rates drop, what each one means for your business, and what to do about it.
Why open rate data is harder to trust than it used to be
Before getting into causes, it is worth understanding how open rate measurement actually works, because this matters.
An open is recorded when a tracking pixel loads inside an email. When Apple launched Mail Privacy Protection (MPP) in 2021, it changed this entirely for a significant proportion of recipients. MPP pre-fetches emails and loads tracking pixels automatically, regardless of whether the recipient actually opens or reads the message.
For UK brands, this is not a minor footnote. Apple devices have high penetration in the UK across both consumer and business markets. In many lists, 40 to 60 per cent of subscribers may be using Apple Mail. That means a large chunk of your "opens" may have been recorded automatically, not by a real person choosing to open your email.
If your open rates dropped around late 2021 or have been inconsistent since, MPP is likely part of the picture. This is not a deliverability issue. It is a measurement issue. But it can look identical to a deliverability problem if you do not know it is there.
This is also why UK open rate benchmarks should be treated with caution. Averages vary significantly by sector, list composition and device split. US benchmark data is even less useful here, as Apple device penetration and inbox behaviour differ between markets.
Reason 1: Your emails are landing in spam or promotions
If your open rates have dropped suddenly, the most important thing to rule out is a deliverability problem.
When emails go to spam, they do not get opened. This shows up as a drop in open rates, but the cause is not engagement. The cause is inbox placement. The emails are being sent, but they are not being seen.
This can happen gradually, as sender reputation erodes over time. It can also happen quickly, following a large send, a sudden volume spike, or an authentication issue that triggers spam filters.
If you have seen a sudden drop rather than a slow decline, deliverability is the first thing to investigate. Check whether your domain appears on any blacklists. Review your authentication setup, which means SPF, DKIM and DMARC. Look at your spam complaint rate if your ESP provides that data.
A decline in inbox placement is a deliverability problem, not a content problem. Changing subject lines or copy will not fix it.
Reason 2: Sender reputation has declined
Sender reputation is how inbox providers assess the trustworthiness of your sending domain and IP. It is built over time and damaged over time.
Reputation damage often shows up as a gradual open rate decline rather than a sudden drop. The signs are subtle at first. Engagement metrics weaken. Fewer recipients interact with your emails. Inbox providers take note. Placement begins to slip.
Common causes of reputation decline include sending to disengaged contacts who have not opened for months or years, high bounce rates from stale or invalid addresses, spam complaints from contacts who cannot easily unsubscribe, and sudden volume increases. That last one is particularly relevant for UK e-commerce brands. The concentration of sending around Black Friday, Christmas and January sales is a common cause of reputation damage. Inbox providers treat unexpected volume spikes with suspicion, particularly from domains that do not usually send at that scale.
If your open rates have been declining over several months rather than dropping overnight, sender reputation is a likely factor.
Reason 3: Authentication is misconfigured
SPF, DKIM and DMARC are the three authentication protocols that prove to inbox providers that your emails are genuinely from you.
When these are misconfigured, inbox providers may treat your emails as suspicious. Emails may be filtered more aggressively, even if your content and list quality are fine.
Authentication issues can develop without any obvious trigger. If you have changed your email service provider, added a new sending tool, or migrated to a new domain, it is worth checking that authentication records are correctly configured and aligned.
DMARC enforcement is increasingly expected by enterprise mail environments, including many UK businesses. If you are not yet at DMARC policy enforcement, it is worth understanding what that means for your deliverability.
Reason 4: List quality has degraded
Every list degrades over time. Contacts change jobs. Email addresses become inactive. People stop engaging without unsubscribing.
Sending to a list with a high proportion of inactive or invalid addresses does two things. It increases your bounce rate, which damages sender reputation. And it pulls down your engagement signals, because non-opens and non-clicks tell inbox providers that your emails are not worth delivering to the inbox.
If your list has grown quickly through sign-up incentives, competitions or third-party sources, the quality may be lower than it appears. Volume is not the same as quality.
Reason 5: Sending behaviour has changed
Open rates respond to changes in how and when you send. If you have recently increased frequency, changed your sending schedule, or shifted the composition of your audience, that may explain a decline.
Sending more frequently does not improve deliverability. If engagement per send falls because you are mailing too often, reputation can decline as a result.
What to do if your open rates have dropped
The first step is to work out which of these causes is most likely, because the fix depends entirely on the cause.
If you suspect a deliverability issue, check your blacklist status, review your authentication records, and look at your spam complaint data if available. If deliverability is the cause, no amount of subject line testing or copy changes will resolve it.
If you suspect sender reputation decline, the approach is not to send more email. It is to reduce volume to your most engaged contacts, let disengaged contacts go, and rebuild your reputation gradually from a cleaner base.
If MPP is distorting your data, open rates are no longer a reliable primary metric. Click rates, conversion rates and revenue per email are more useful indicators of whether your emails are actually working.
If you are not sure which of these applies, a deliverability audit will tell you. It looks at your authentication, reputation, blacklist status, list quality and sending behaviour, and gives you a clear picture of what is actually causing the problem.
Digistrat works with UK SaaS, app-based and e-commerce businesses to diagnose and fix email deliverability issues. If your open rates have dropped and you want to understand why, a Deliverability Audit is the right starting point.
