smtp bounce code
550 5.7.606Access denied, banned sending IP
what to do
Keep the address, fix your side
Microsoft has blocked your sending IP. Every message to any Microsoft 365 tenant will fail until it is delisted.
What the server is telling you
The IP you are sending from is on Microsoft's block list. It says nothing about the recipient, and it will not resolve by retrying.
Next steps
- →Do not suppress anything.
- →Submit a delisting request to Microsoft.
- →Review what was sent from that IP. Something triggered it.
Commonly returned by: Microsoft 365
Find these before you send, not after
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