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#
- Verifying the root domain but sending from an unverified subdomain.
- Reading reputation as a single day rather than a trend.
Fix and re-verify#
- Add your sending domain and verify with a TXT record.
- Send consistently for a few days so data appears.
- Check spam rate daily; stay under 0.1% and never above 0.3%.
- Investigate any day domain reputation drops from High.
- Correlate authentication failures with new sending sources.
Frequently asked questions#
Why is Postmaster Tools empty?
Volume is too low for Gmail to report, the domain is not verified, or you are looking at the wrong domain (From versus DKIM d=).