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550 5.7.606 Access denied, banned sending IP

Microsoft banned the sending IP address

Seen in Microsoft 365, Outlook.com, Hotmail (inbound)

Microsoft's filtering has put your sending IP on its block list (5.7.606 to 5.7.649, or 5.7.511 banned sender), so mail from it to Microsoft-hosted recipients is refused.

Common causes

  • The IP sent spam, often from a compromised account, website form or server.
  • A shared or newly assigned IP inherited a poor reputation.
  • Poor list hygiene caused high complaint or invalid-recipient rates.

How to fix it

  1. Fix the source of the bad mail first, or delisting will not stick.
  2. For 5.7.606 to 5.7.649, request removal at the Microsoft delist portal (sender.office.com).
  3. For 5.7.511, email delist@microsoft.com with the full NDR and the IP address.
Look up the sending IP

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Related errors

All 33 Email (SMTP) errors