SMTP error X.2.0
Other or undefined mailbox status
Updated Jul 1, 2026
The short answer
Other or undefined mailbox status Common cause: Mailbox exists, but an unspecified mailbox problem occurred
Quick fix
Check the detailed bounce text or contact the recipient
2 - Success. Not an error - the server accepted or completed the action.
This code is written X.2.0 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
Check the detailed bounce text or contact the recipient