Dedicated IP addresses 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#

• Buying a dedicated IP for a small list and letting it go cold.
• One dedicated IP for everything, so a promo blast delays receipts.

Fix and re-verify#

1. Estimate steady daily volume; below roughly 50,000 per day, shared pools usually perform better.
2. If dedicated, warm up over 4 to 6 weeks and keep volume consistent.
3. Separate transactional and marketing onto different IPs or pools.
4. Monitor SNDS and Postmaster Tools per IP.

Frequently asked questions#