Let me go back and ask in your current setup did you authorize as a different account than the email? If so we’ve seen a bug where it’s using the Authorizer's account to attempt to connect to IMAP/POP3 and SMTP. We are working on a patch to address this and I’ll let you know once that’s available.
To test this try adding the email as an Application Admin (meaning they are admin only for this app) and consent/authorize as the email itself. If that works then your issue is definitely what I mentioned above.
Cheers.