Spam complaints

A complaint is a recipient pressing "report spam". It is the single most damaging signal in email, and the tolerances are far tighter than most people expect.

The numbers

• 0.03% is a warning.
• 0.08% stops a campaign for review.

0.08% is roughly one complaint in twelve hundred. Ten complaints on a ten-thousand send is enough to be a problem.

Compare that with bounces, where the equivalent line is 4% — fifty times more tolerant. Providers treat "this person did not want your mail" far more seriously than "this address does not exist".

What complaints actually mean

Almost never "this email was offensive". Nearly always "I do not remember signing up for this":

• The list is old and people have forgotten you.
• Consent was unclear — a checkbox pre-ticked, or an address collected for one purpose and used for another.
• The content does not match what people expected when they subscribed.
• Sending is infrequent enough that each email arrives as a surprise.

Why unsubscribes are better than complaints

Both remove the person. Only one damages you.

So make unsubscribing easy and obvious. A hidden or awkward unsubscribe link does not keep subscribers — it converts them into complainers, and every complaint costs you delivery to everyone else.

Reducing complaints

• Send consistently. A monthly email people expect beats a surprise every six months.
• Match the promise. If people subscribed for discounts, send discounts.
• Remove dormant contacts before they remove themselves. Someone who has not opened anything in a year is far likelier to complain than to buy.
• Never re-add someone who opted out. Re-importing them from a CSV does not restore consent, and it is the fastest route to a complaint.

Next: if a campaign was stopped for complaints, look at where that audience came from before resuming — see Why is my campaign paused?.