We are unable to send emails through manager.io. When this kind of server error was came in past, we normally had to change his email password. While we have also changed email’s password. This error came in last week. Please suggest to fix this error. See below error screenshot for reference.
This error is not from Manager. It’s from Office 365 servers. We are just relaying it.
The error says SMTP is disabled and there is a link https://aka.ms/smtp_auth_disabled for more information.
I suggest read that or contact Microsoft / Office 365 support.