I have been using TB to access my Exchange accounts at work through IMAP and OAuth2. Last week this stopped working and the server reports this: 'AADSTS7000112: Application '9e5f94bc-e8a4-4e73-b8be-63364c29d753'(Thunderbird) is disabled.' IT say they won't re-enable access for individual users. I know TB's native support for Exchange is coming and that may solve the problem but in the meanwhile I notice my K-9 Mail on Android still works fine even though it is set up as TB. The only difference is that K9 is set up to hide the identity of the mail client in outgoing mail headers. This and that the error message above specifically mention Thunderbird make me think: Could I perhaps bypass the block if the server didn't know I was using TB? Is there a way to get TB to spoof or withhold its identity? This is clearly not about not reporting the mailer in the headers as it seems the server can tell the agent on connection (ID '9e5f94bc-e8a4-4e73-b8be-63364c29d753' as mentioned here: https://support.mozilla.org/en-US/kb/microsoft-oauth-authentication-and-thunderbird-202 ).