How to get delisted from Microsoft (Outlook.com / Hotmail)

Not a public blocklist — Microsoft blocks by internal sender reputation (bounce codes like S3140).

Fix the cause first

1. Meet Outlook's sender requirements first: since May 2025, senders over 5,000 messages/day must pass SPF, DKIM AND DMARC or their mail is rejected outright (bounce code 550 5.7.515). Fix authentication and complaint sources before asking for mitigation.

Mitigation is discretionary and reputation-based — blocks come back if complaints continue.

Then request removal

1. For Outlook.com/Hotmail blocks (S3140-style bounces): file the sender support form at olcsupport.office.com — it requires signing in with a Microsoft account.
2. Expect an automated "not qualified for mitigation" first reply; respond with specifics (IP, exact bounce text, volumes, what you fixed) to reach human review.
3. For Microsoft 365 "banned sending IP" blocks (bounce codes 5.7.606–649) there's a separate official delist portal at sender.office.com. A 5.7.511 bounce CANNOT use that portal — Microsoft's instruction is to email delist@microsoft.com with the full NDR text and your IP; they say they respond within 48 hours.
4. Enroll in SNDS and JMRP at the postmaster site so you can see your IP's reputation and complaints going forward.

Cost: Free.

Before any delisting request — the fundamentals

• ·Find and clean the actual source: compromised accounts or machines, malware, insecure web forms, open relays or proxies (many "open relays" turn out to be infected machines).
• ·Set up SPF and DKIM on everything that sends, and publish DMARC.
• ·Give every sending IP meaningful, matching forward and reverse DNS (PTR).
• ·Make sure abuse@ and postmaster@ addresses exist, are monitored, and never bounce.
• ·Only then request delisting where the operator offers it — every major operator relists automatically (or keeps filtering) while the cause persists.

Process verified against the operator's own pages on 2026-07-12.