Authentication on SMTP to Microsoft Outlook using OAuth about mailkit HOT 1 CLOSED

Yes, it is supposed to work but you aren't the first (and won't be the last) person to struggle with this.

OAUTH2 is a nightmare to get working and Office365, for whatever reason, seems to take the cake especially for the confidential-client flow. I get multiple emails, bug reports, and/or StackOverflow questions per week on this topic and I honestly have no idea how to provide a solution for people so that I can finally end the nightmare.

From a quick glance at your code, it looks like you at least followed the directions in my ExchangeOAuth2.md documentation.

All I can suggest is reading and rereading the documentation I wrote up (which tries to simplify the process) and Microsoft's own dizzyingly (is that a word? it should be) confusing documentation to try and figure out what step you missed.

If you've got access to Microsoft Support, I'd recommend cashing in on that support contract and getting help from someone on the Office365 support team and making them earn their keep.

from mailkit.