Why Did This Email Fail?

Enter the status code from a bounce message, or paste the bounce message and we'll find the code in it.

This looks up the code against the IANA SMTP Enhanced Status Codes Registry and RFC 5321 basic codes — it doesn't attempt to parse the rest of a bounce message's wording, since bounce formats vary too much across mail servers and providers for that to be reliable. A code is the one part of a bounce message that's actually standardized, so that's what this tool relies on.

Status code

Formats: 550 · 550 5.1.1 · 5.1.1

Paste the bounce message

We scan the pasted text for the first standard code pattern (e.g. "550 5.1.1") — not a full read of the message. If a message contains more than one code, only the first match is used.

Enter a code above, or paste a bounce message, to see the explanation here.