Thunderbird OAuth2 does not work for Shared Mailboxes on O365
Microsoft is enhancing security and disabling Username/Password in favor of OAuth2 authentication. While this works for the primary account, Shared Mailbox accounts will not connect with OAuth2. There is a temporary solution to re-enable the legacy authentication, but this too will be disabled in September, 2022 (according to MS Support).
Reference Pages: Setting up Shared Mailbox in Thunderbird: https://www.en.its.aau.dk/instructions/Mail/shared-mailbox-thunderbird/
Microsoft is enhancing security and disabling Username/Password in favor of OAuth2 authentication. While this works for the primary account, Shared Mailbox accounts will not connect with OAuth2. There is a temporary solution to re-enable the legacy authentication, but this too will be disabled in September, 2022 (according to MS Support).
Reference Pages:
Setting up Shared Mailbox in Thunderbird:
https://www.en.its.aau.dk/instructions/Mail/shared-mailbox-thunderbird/
MS OAuth2 Guide:
https://docs.microsoft.com/en-us/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth#sasl-xoauth2-authentication-for-shared-mailboxes-in-office-365