Symptoms#
- Messages landing in spam despite previously good placement
- Bounces mentioning policy, authentication, or reputation
- Provider dashboards showing a drop in reputation or authentication pass rate
Diagnosis steps#
- Confirm the configuration is live: query DNS from an external resolver and check the sending platform's settings page.
- Send to a seed mailbox and read the full headers, especially Authentication-Results.
- Compare the domains in From, Return-Path, and DKIM d= for alignment.
- Check provider dashboards (Google Postmaster Tools, Microsoft SNDS) for reputation and error rates.
- Review recent changes: new vendors, DNS edits, list imports, volume spikes.
Likely causes#
- Importing old exports without verification.
- Keeping unengaged contacts because the list size looks good in reports.
Fix and re-verify#
- Verify new signups in real time with an API and use double opt-in for marketing lists.
- Suppress hard bounces immediately and soft bounces after 3 consecutive failures.
- Run a re-engagement campaign at 90 days of inactivity and sunset at 180.
- Remove role accounts (info@, sales@) and disposable domains from marketing lists.
- Audit the list quarterly with a bulk verification service.
Frequently asked questions#
What is a spam trap?
An address that never opted in, maintained by providers and blocklists to catch senders with poor acquisition practices. Hitting one can blocklist your IP or domain.
What bounce rate is acceptable?
Under 2% hard bounces. Above 5% typically triggers ESP account reviews.