(In reply to Thunderbird Addicted from comment #33) > Basically, Thunderbird does not fully support Microsoft's Modern authentication: Office365-based corporate email accounts will not be able to send messages if Basic authentication has been disabled (as security defaults are enabled) in the organization If you can point to something in Microsoft's documentation or elsewhere that actually explains what we're not doing, that'd be helpful. "Doesn't support" this or that is unfortunately not enough information to fix any remaining bug here. Note that Oauth2 SMTP works completely fine with M365 standard accounts which is what we've got to test on. I'm honestly not even sure anyone at Microsoft understands app of their word salad security theatre approach to OAuth2.
Bug 1775077 Comment 35 Edit History
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(In reply to Thunderbird Addicted from comment #33) > Basically, Thunderbird does not fully support Microsoft's Modern authentication: Office365-based corporate email accounts will not be able to send messages if Basic authentication has been disabled (as security defaults are enabled) in the organization If you can point to something in Microsoft's documentation or elsewhere that actually explains what we're not doing, that'd be helpful. "Doesn't support" this or that is unfortunately not enough information to fix any remaining bug here. Note that Oauth2 SMTP works completely fine with M365 standard accounts which is what we've got to test on. I'm honestly not even sure anyone at Microsoft understands all of their word salad security theatre approach to OAuth2.