Update: The full timeline for retirement of Basic Authentication in Exchange Online is now published in Basic Authentication Deprecation in Exchange Online – September 2022 Update.
It’s been a few ...
Updated Sep 01, 2022
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Jason_Gunthorpe I see, thanks, that's an issue. With no actual OAuth available for IMAP in O365 as it seems there's no way the whole world will be able to support it until October. https://bugzilla.mozilla.org/show_bug.cgi?id=1528136 the Thunderbird issue about this.
ph_ly in Thunderbird IMAP uses the same authentication options as POP3 I think, which is basic auth and OAuth2, among others. If OAuth won't work with Thunderbird then that means that it won't support O365 at all (apart from with paid add-ons) come October.
BTW apart from the examples mentioned here already, CRM tools with e-mail integration are another area where both IMAP, and in the future SMTP will need to be patched.