550 5.7.606–649: banned sending IP: use the delist portal
Microsoft 365 put your sending IP on its blocked senders list; you can request removal yourself at sender.office.com.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.606–649
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 5.7.606 Access denied, banned sending IP [IP1.IP2.IP3.IP4]
What it means
Microsoft 365 keeps a blocked senders list of source IPs it considers a threat to its customers. Mail from a listed IP is refused with a code between 5.7.606 and 5.7.649, and the bounce points to the Office 365 Anti-Spam IP Delist Portal at sender.office.com. The portal is self-service: you confirm an email address, then delist the IP. Removal can take 24 hours or longer, and the IP can be listed again if the traffic stays abusive. The portal covers Microsoft 365 recipients only; Outlook.com blocks go through the Outlook.com sender support form, and 5.7.511 goes to delist@microsoft.com.
Common causes
- The IP sent spam, phishing or other unwanted mail to Microsoft 365 recipients.
- The IP is shared, and another sender on it caused the listing.
- A compromised account, server or open relay on your network sent from the IP.
How to fix it
- 01Check that traffic from the IP is clean: look for compromised accounts, open relays and spikes in volume.
- 02Go to sender.office.com, enter the email address that received the bounce and the IP from the error, and submit.
- 03Open the confirmation link sent to that address, then select Delist IP.
- 04Allow 24 hours or more, and keep following deliverability best practices so the IP is not listed again.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- External senders: use the delist portal to remove yourself from the blocked senders list and address 5.7.511 Access denied errorslearn.microsoft.com
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
- External senders: troubleshoot email sent to Microsoft 365learn.microsoft.com
Related codes
- 550 5.7.511Banned sending IP: request removal by email.Microsoft 365 banned the IP you send from and wants to investigate before lifting it; the delist portal cannot remove this block.
- 5.7.1Sending IP on the Microsoft 365 blocklist.Microsoft 365 refused the message because the sending IP address is on its own blocklist, named Blocklist 1 in the bounce.
- 550 5.7.708Traffic not accepted from this IP.Microsoft 365 refused mail from the sending IP because of its low reputation; Microsoft says new tenants such as trials are most affected.
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce