Message Not Delivered: User authentication for message failed
The message could not be delivered because there was a problem with the sender's user authentication to the sender's email provider email system.
Review the email account settings. Check for options that require "user authentication" for outbound SMTP and ensure that the Username and Password values are correct.
If the account settings are correct, contact the email provider to help identify any misconfiguration with the sender's account or with the email system.
5.7.4: Official Definition
A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery.
A message contained security features such as secure authentication that could not be supported on the delivery protocol. This is useful only as a permanent error.