Office 365: Basic Auth is disabled


Since October 2022 Basic Auth is by default disabled for IMAP and POP3 in Exchange Online / Office 365. Microsoft recommends using OAuth 2.0. This is not a big problem for Mail.dll email client for .net users as it support OAuth 2.0 in full.

Auth 2.0

You should switch to OAuth 2.0 for authentication purposes:

Daemons/Services: Password grant (MFA/2FA must be turned off for this account):
https://www.limilabs.com/blog/oauth2-password-grant-office365-exchange-imap-pop3-smtp

Daemons/Services: Client credential flow:
https://www.limilabs.com/blog/oauth2-client-credential-flow-office365-exchange-imap-pop3-smtp

Web apps (requires user interaction):
https://www.limilabs.com/blog/oauth2-web-flow-office365-exchange-imap-pop3-smtp

Standalone devices (requires very little interaction):
https://www.limilabs.com/blog/oauth2-device-flow-office365-exchange-imap-pop3-smtp

Desktop apps (requires user interaction):
https://www.limilabs.com/blog/oauth2-office365-exchange-imap-pop3-smtp

Re-enable Basic Auth

For some time it was possible to re-enable Basic Auth for IMAP and POP3 for your tenant – it is no longer possible to do that.

Questions?

Consider using our Q&A forum for asking questions.