Bulk sender requirements not working? Troubleshooting guide

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#

1. Confirm the configuration is live: query DNS from an external resolver and check the sending platform's settings page.
2. Send to a seed mailbox and read the full headers, especially Authentication-Results.
3. Compare the domains in From, Return-Path, and DKIM d= for alignment.
4. Check provider dashboards (Google Postmaster Tools, Microsoft SNDS) for reputation and error rates.
5. Review recent changes: new vendors, DNS edits, list imports, volume spikes.

Likely causes#

• Thinking the rules only apply above 5,000; Gmail applies most of them to all senders.
• Using a gmail.com From address for bulk mail, which fails DMARC alignment.

Fix and re-verify#

1. Publish SPF and DKIM, and a DMARC record at minimum p=none with aligned From domain.
2. Add List-Unsubscribe headers and honor requests within two days.
3. Use a valid forward and reverse DNS (PTR) for sending IPs.
4. Monitor spam rate in Postmaster Tools and keep it under 0.1%.
5. Send from a subdomain with its own reputation for marketing.

Frequently asked questions#