Today, we started to disable basic authentication for any protocol not opted-out prior to September 30, 2022.
For more information see the “Basic Authentication in Exchange Online - 7 Day Notice” notification in Message Center.
If you need to re-enable a protocol, you can do so once by following the process here.
Please verify your clients are using clients configured with Modern Authentication.
Outlook 2013 – Office 2013 client applications utilize legacy authentication by default. Users may need to update their registry to fully enable Modern Authentication. Please reference this document for more information.
Exchange ActiveSync – Users may need to remove and re-add their account to fully switch to Modern Authentication on mobile devices using EAS protocol.
POP/IMAP clients – If your POP/IMAP clients or apps are unable to connect, you might need to change your email client to one that supports Modern Authentication (Outlook does not support Modern Authentication for POP/IMAP accounts), or switch to Outlook on the web. You can use your browser and access Outlook on the web via https://outlook.office.com.