DIAGNOSTIC PLAYBOOK
Spam complaint rates: check the denominator before comparing
Complaint rates from different reports can use different denominators and coverage. A numerical change may reflect a different measured population rather than a proportional change across all mail.
HealthCheck Email editorial team · · Examples are illustrative
How to investigate
- Write down the source, reporting period, eligible traffic and denominator for each rate.
- Compare like-for-like segments and preserve any missing-data or minimum-volume limitations.
- Investigate the campaign or recipient segment connected to a real increase before generalizing to the entire domain.
What this looks like
ILLUSTRATIVE EXAMPLE
One system divides complaints by delivered campaign mail while another reports its own eligible mailbox population. Equal percentages need not represent equal events.
A mistake to avoid
Do not combine rates by averaging percentages. Compatible underlying counts and definitions are required for a meaningful aggregate.
Keep the result in context
A successful handoff, a delivered event and an inbox placement are different observations. Record the receiving provider, send time, SMTP response and affected stream before comparing results. DNS fixes address authentication or routing; they cannot establish consent or guarantee placement.
Take the next step
Use the related check to gather evidence, then compare it with the affected message or service. Keep the result and time with your notes so a later change can be distinguished from the original problem.
Sources and further reading
The protocol references below explain the underlying behavior. Your sending or DNS provider supplies the account-specific settings for its service.