550 error: Requested action not taken - permanent failure
The generic permanent rejection. It can mean a bad mailbox, a blocklist, failed authentication or spam filtering - the enhanced code and text next to it say which.
How to fix 550
- Find the x.y.z status code (like 5.1.1 or 5.7.1) in the same message and decode it.
- Don't retry the same message; fix the cause first.
Why this happens
The receiving server refused the message under a policy rule and the code alone doesn't say which one. The explanatory text after the code is where the actual reason - a blocklist, authentication, content or reputation - is named.
How to keep it from coming back
Keep authentication correct, stay off blocklists, send to engaged recipients and test messages before sending. Always keep the full bounce text, because it is what identifies the rule that fired.
Should I retry a 550 error?
Not as it stands. A permanent error means the same message will be refused again until the cause is fixed on your side. Fix the cause first, then send a fresh message; if it keeps failing after that, check the full text of the bounce for the exact reason.
Got the full bounce message?
The text after the code names the exact reason, and the same code can mean different things at different receivers. Paste the whole message into the decoder - it runs in your browser and nothing is sent.
Open the bounce decoderRelated error codes
Seeing this again and again? That's usually a reputation or authentication problem we can trace and fix at the source.
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