My open rate suddenly dropped

A drop in open rate can mean several different things. Before trying to fix it, it helps to understand what actually changed. Work through the questions below to identify the cause.

First: is the drop real?

Open rate measurement became less reliable in September 2021 when Apple introduced Mail Privacy Protection (MPP). MPP automatically pre-loads email content for Apple Mail users, registering a "open" even if the recipient never actually read the message. This inflated open rates for many senders.

If your open rate was unusually high before and has now come down, the drop may reflect a more accurate picture of your actual readership, not a real decline in engagement.

Check what changed between campaigns

Compare the underperforming campaign with your last several campaigns that performed normally. Look for differences in:

• Sender name or sender address: a change here is the most common cause of a sudden open rate drop. If recipients no longer recognise who the email is from, they will not open it.
• Subject line: a weaker or more generic subject line directly affects open rate.
• Sending time or day of the week: open rates vary significantly by day and time.
• Target group or segment: if you sent to a different segment, a different contact profile, or a much larger or smaller audience than usual, the rate will be different.
• Sending frequency: if you sent multiple campaigns in a short period, recipients may be less likely to open the most recent one.

Check your list health

A deteriorating list affects open rates over time. Look at your campaign reports for:

• Rising bounce rate: a growing number of undeliverable addresses means your list contains stale contacts. High bounces also damage your sender reputation, reducing inbox placement.
• Rising unsubscribe rate: contacts are opting out faster than normal, which may indicate your content is no longer relevant to your audience.
• Spam complaints: even a small number of spam complaints damages your deliverability. Contacts who mark your email as spam are automatically blacklisted.

Go to Contacts > All contacts and check the Blacklisted tab. A growing blacklist after recent campaigns indicates list quality issues.

Check your deliverability signals

If your emails are landing in spam rather than the inbox, your open rate will drop because recipients simply never see them. Check:

• Go to Settings > Add or remove senders and confirm all three authentication records (SPF, DKIM, DMARC) are still green. Authentication records can stop working if your domain DNS settings were changed.
• Check whether your sender address or sending domain was recently changed.
• Run a message check on your most recent message to look for content-level spam signals.

If you suspect a deliverability issue, see "My emails are landing in spam" for a full diagnosis checklist.

One-off drop vs. sustained decline

A single campaign with a lower open rate is usually not a cause for concern. Open rates naturally vary between campaigns based on topic, segment, and timing. Look for a pattern across three or more consecutive campaigns before drawing conclusions.

Use the Ratios section in your campaign report to compare performance against your account average. This gives context for whether a result is genuinely below your normal range.

Common mistakes to avoid

Comparing open rates across different segments

A campaign sent to your most engaged subscribers will have a higher open rate than one sent to your full list. Only compare campaigns sent to the same or equivalent audiences.

Making multiple changes at once

If you change your sender name, subject line, and sending time all at once, you will not be able to identify which change caused the difference in open rate. Change one variable at a time when testing.

Reacting to a single campaign result

One lower-performing campaign is not a trend. Review your results across at least three to five campaigns before making strategic changes to your sending approach.

Next steps

• See "Campaign reports" for a full explanation of how to read and interpret your campaign metrics.
• See "My emails are landing in spam" if you suspect a deliverability issue.
• See "Email frequency" for guidance on finding the right sending cadence for your audience.
• See "AB testing" if you want to systematically test subject lines or content to improve performance.