Diagnosing High Complaint Rates

Diagnose and fix high complaint rates

Diagnosing High Complaint Rates

A complaint occurs when a subscriber marks your email as spam in their email client. High complaint rates are the fastest way to damage your sender reputation and get your emails filtered to the spam folder. Mailnaptic monitors complaint rates continuously and alerts you when thresholds are crossed.

What is a healthy complaint rate?

Industry best practice is to keep your complaint rate below 0.1% (1 complaint per 1,000 emails sent). At 0.5% and above, your sender reputation is at critical risk, and major mailbox providers like Gmail will begin aggressively filtering your emails.

Mailnaptic's platform-level complaint alerting logs a warning at 0.1% and an error at 0.5%. These thresholds are checked every monitoring cycle by the domain monitor worker.

Checking your complaint rate

1. Go to Organization Settings and scroll to the Deliverability section.
2. Review the complaint rate for each sending domain.
3. Check the ISP Stats breakdown to see if complaints are concentrated at specific mailbox providers.

Common causes of high complaint rates

1. Purchased or scraped email lists

Contacts who never opted in to receive your emails will mark them as spam. Never import purchased, rented, or scraped email lists. Every contact should have explicitly consented to receive your emails.

2. Unclear sender identity

If subscribers do not recognize who an email is from, they are more likely to report it as spam. Use a consistent and recognizable "From" name and email address.

3. Sending too frequently

Subscriber fatigue leads to complaints. If you have recently increased your sending cadence, enable frequency capping in Organization Settings to limit how many emails each contact receives per time period.

4. Difficult or hidden unsubscribe link

When subscribers cannot easily find your unsubscribe link, they use the spam button instead. Mailnaptic includes a List-Unsubscribe header and one-click unsubscribe support. Make sure your unsubscribe link is prominent in the email body as well.

5. Stale or old lists

If you have not emailed your list in months and then resume sending, many subscribers will have forgotten they signed up. Re-engage stale lists gradually with a re-permission campaign.

6. Misleading subject lines

Subject lines that do not match the email content feel deceptive and trigger complaints. Ensure your subject line accurately reflects what the email contains.

Steps to fix a high complaint rate

1. Pause sending — If your complaint rate is above 0.5%, stop sending campaigns until you have identified and addressed the cause.
2. Review recent campaigns — Look at which campaigns generated the most complaints. Check the campaign activity log for complaint events.
3. Check the ISP breakdown — If complaints are concentrated at one provider, investigate provider-specific issues.
4. Clean your list — Remove contacts who have not engaged in the last 90-180 days. Use Mailnaptic segments with engagement filters like email_not_opened to identify inactive contacts.
5. Enable double opt-in — Require new subscribers to confirm their email address before receiving campaigns.
6. Enable frequency capping — Prevent over-sending to individual contacts.
7. Improve your unsubscribe experience — Make unsubscribing easy and instant. A clean unsubscribe is far better than a spam complaint.

Recovering from a high complaint rate takes time. Mailbox providers need to see sustained improvement in your complaint rate over multiple weeks before they will restore your reputation.