Microsoft has set the deadline for their deprecation of Basic/Simple Authentication for SMTP (SMTP AUTH). WebHelpDesk does not support OAuth 2.0, which will be REQUIRED for Office 365. Support for OAuth 2.0 must be added to WebHelpDesk by September 2025, or the product must be abandoned.
Deprecation of Basic authentication in Exchange Online | Microsoft Learn
Exchange Online to retire Basic auth for Client Submission (SMTP AUTH) - Microsoft Community Hub
