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Email error codes

Bounce codes, explained

A bounce message is the receiving server telling you why it did not deliver your email. Find your code to see what it means, who is at fault and how to fix it.

Permanent errors: the address or domain is not valid

550 5.1.1Mailbox does not exist (user unknown) 550 5.4.1Recipient address rejected (access denied) 553 5.1.3Invalid address syntax 550 5.2.1Mailbox disabled or not accepting mail 550 5.1.2Bad destination domain (domain not found)

Temporary errors: try again later

552 5.2.2Mailbox full (over quota) 421 4.7.0Try again later (rate limited or deferred) 450 4.2.1Mailbox temporarily unavailable 451 4.7.1Greylisted (try again later) 452 4.2.2Insufficient storage or too many recipients 421 4.4.1Connection timed out

Sender and policy errors: fix your setup

550 5.7.1Rejected by policy (blocked) 550 5.7.26Sender not authenticated (SPF, DKIM, DMARC) 554 5.7.1Transaction failed (blocked or service unavailable) 535 5.7.8Authentication failed (SMTP login) Spam rejectionMessage flagged as spam

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