550 5.7.606-649 Access denied, banned sending IP [IP address]
Sample bounce line
550 5.7.606-649 Access denied, banned sending IP [203.0.113.10]: To request removal from this list please visit https://sender.office.com/ and follow the directions. For more information, see Email non-delivery reports in Exchange Online.
What it means
The IP address you are sending from is on Microsoft 365's blocked senders list. Microsoft uses the list to protect customers from spam, spoofing, and phishing, and adds a source IP identified as a potential threat.
Why it happens
- The sending IP was banned.
- The IP's reputation may be degraded because of compromise or malicious traffic.
How to fix it
- Verify you follow the best practices for email deliverability, and make sure your IP's reputation isn't degraded by compromise or malicious traffic.
- If the ban is in error, use the Office 365 Anti-Spam IP Delist Portal at https://sender.office.com.
- In the portal, enter the email address that received the NDR and the IP address from the error message. Only one email address and one IP address are allowed per visit.
- Select Submit, select the confirmation link in the email you receive, then select Delist IP in the portal.
- Results can take up to 24 hours or longer. Mail is delivered once the IP is removed and it passes Microsoft's security checks. Abusive or malicious traffic can get the IP blocked again.
Check your domain now
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