Announcing OAuth 2.0 Client Credentials Flow support for POP and IMAP protocols in Exchange Online

My SMTP basic authentication access for my emailing application was disabled in the middle of September and I had to get my Administrator to re-enable it system-wide.   They were not happy about doing this however I still have users that need to use this application.   I am in the process of converting this application to use Modern Authentication after my Administrator configured my application in Azure.   I have it coded to return the bearer token that I then pass into Java Mail.   It all looks correct, however I continually get "535 5.7.3 Authentication unsuccessful" failures when I try to send a test email.

Is this error because SMTP Credential Flow is still not enabled, or is there something else that I'm missing?  It would be nice if the "535 5.7.3 Authentication unsuccessful" failure provided a little more information about the failure.