Troubleshooting SMTP Setup Error on Office365.com: Resolving EHLO Message Failure (535 5.7.139) - Authentication Unsuccessful, Basic Authentication Disabled

Error:

SMTP server 'smtp.office365.com' tested: Failure on EHLO message to server - 
535 5.7.139 Authentication unsuccessful, basic authentication is disabled.

Solution:

Microsoft deprecated Basic Authentication as the default setting for O365 in October of 2023 and Cerberus now supports Microsoft OAuth2 for O365 SMTP Authentication. You can now refer to the “Configuring Microsoft OAuth2 Authentication”' section of this article to configure your SMTP integration: How do I setup SMTP to send Email notifications?