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#
- Trusting a vendor's 'verified' label from months ago.
- Treating catch-all as valid.
Fix and re-verify#
- Verify every address through an API before it enters a sequence.
- Segregate catch-all domains and send to them at lower volume.
- Refresh verification for any lead older than 90 days.
- Enrich with 3 to 5 data points that drive the opening line.
Frequently asked questions#
What bounce rate is safe for cold email?
Under 2 percent. Above 5 percent, pause and re-verify the list before continuing.