Bounce codes › Microsoft 365
550 5.7.511: Access denied, banned sender
Microsoft has banned the IP address your email was sent from. Every message from that IP to Microsoft 365 is refused.
Fix your sending setup Your sending IP or domain is blocked
Microsoft banned the IP address you send from.
- Sent by: Microsoft 365 / Outlook
- Permanent (hard bounce). Sending the same message again fails again.
How Microsoft 365 words it (source):
Access denied, banned sender
Why it happens
- The IP sent a lot of mail that Microsoft users marked as spam.
- The IP sent to many addresses that do not exist.
- It is a shared IP at your email service and another customer caused the ban.
What to do
- Forward the full bounce message, with the IP address, to
[email protected]. Microsoft names this address in its documentation for this code. - If you use an email service, send them the bounce: the IP is theirs to delist.
- Before you ask, clean up what caused it. Check your list for dead domains and typos, and stop sending to people who did not sign up.
Don't confuse it with
550 5.7.606 to 5.7.649 is also a banned IP, with a self-service delist portal. 550 5.7.513 is a block set by one recipient company, not by Microsoft.
Questions
Are the recipients' addresses bad?
No. Keep them. The block is on your sending IP.
How long does delisting take?
Microsoft does not promise a time. Expect a day or more.
Got a different bounce?
Paste the whole message into the bounce code lookup. It reads the code and the words and tells you whose move it is.
Related codes
550 5.7.606Access denied, banned sending IP (Microsoft 365)550 5.7.1This message is likely unsolicited mail (Gmail)