Enhanced status code

SMTP error X.3.6

Requested priority changed

Updated Jul 1, 2026

The short answer

Requested priority changed Common cause: Message was accepted but priority was altered

Quick fix

Usually no action required

This code is written X.3.6 because the reason is the same whether the failure is temporary (a 4 first digit) or permanent (a 5). Read the first digit of your own bounce to know which applies.

How to fix it

Usually no action required

Related codes

X.3.0 Other or undefined mail system status X.3.1 Mail system full X.3.2 System not accepting network messages X.3.3 System not capable of selected features X.3.4 Message too big for system X.3.5 System incorrectly configured
All SMTP error codes
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Most rejections come back to sender reputation.

Blocklists, auth failures, and policy blocks are what warmup prevents. Warm up your domain so your mail is trusted before you hit send.

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