As some of you are aware, Microsoft is pushing organizations to keep elevating their security posture. Some changes might affect your entire organization and leave your users, applications, and services without mail flow.
On Oct. 1 of this year, Microsoft turned off Basic Authentication in several products, including:
Exchange Online for Exchange ActiveSync (EAS)
Exchange Web Services (EWS)
Offline Address Book (OAB)
Outlook for Windows and Outlook for Mac.
Microsoft also disabled SMTP AUTH in all tenants in which it was not being used. This decision required customers to move from applications that use Basic Authentication to those that use Modern Authentication. Effective Jan. 1, 2023, these protocols will be permanently disabled for Basic Authentication, and Basic Authentication will be unavailable after this date. All tenants currently on Basic Authentication must move to Modern Authentication by upgrading client software.
You can check your users’ Authentication Dialog Box, Message Center, Admin Center, or Azure Active Directory Sign-in Report to see if your tenant is still on Basic Authentication. For more information, read the following links or contact us at firstname.lastname@example.org • Basic Authentication in Exchange Online gone | Microsoft 365 Blog • Deprecation of Basic authentication in Exchange Online | Microsoft Learn