I have logged in as admin and set this address to have sync and IMAP enabled.
https://www.screencast.com/t/6c51C7cE

I have generated an app specific password.  A couple of times..

Problem is when trying to add new IMAP account, Thunderbird keeps saying the password or username is incorrect.  I am using the generated App specific password, and  user@domain.com

https://www.screencast.com/t/iOhdwwNfpYw

If I change to POP3 with same info, it works.  except when sending outbound to a different domain name.

Any ideas?