5.2.1 error: Mailbox disabled or not accepting mail
The mailbox exists but is deactivated, suspended or set not to accept messages - often a former employee's address.
How to fix 5.2.1
- Treat it as undeliverable and remove it.
- If it should work, the recipient's admin has to re-enable it.
Why this happens
The recipient's mailbox itself can't take the message right now - it is full, disabled or temporarily unavailable. It has nothing to do with your content or reputation.
How to keep it from coming back
You can't prevent a recipient's full mailbox, but you can avoid sending repeatedly to addresses that keep returning it, and remove them if the error persists across several attempts.
Should I retry a 5.2.1 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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