Exchange Online to retire Basic auth for Client Submission (SMTP AUTH)

Hoegi71 the endpoint smtp.office365.com will still be available but you will not be able to use basic auth as the authentication method. Please review this document then follow up if you still have questions: Deprecation of Basic authentication in Exchange Online | Microsoft Learn

johndfe36540 great question! HVE will continue to support Basic Auth. HVE sends using an HVE account and not a cloud-hosted mailbox, so the only abuse from a compromised HVE account would be using the account to send spam internal to the tenant. This creates isolation, and there are significant security benefits from removing basic auth from SMTP AUTH which does use cloud-hosted mailboxes for sending. 

jc98jc thanks for the question! So, you can/should use OAuth if your device supports it: https://learn.microsoft.com/en-us/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth. Otherwise, those are the key methods that we have planned currently, no others.  Is there a specific alternative your organization is looking for?