The server rejected our credentials.

Either the username, password, or challenge response given to the server was rejected.

This is considered a non-fatal error (the connection will not be dropped).

Inherited from SMTPClientError (via ESMTPClientError):

Method __init__
Method __str__ Undocumented
Method __bytes__ Undocumented
API Documentation for Twisted, generated by pydoctor at 2018-04-29 21:01:12.