1) if telnet on port 25 fails , as email bounced back, or if I get 421 error or similar
what troubleshooting steps should I look for . I heard some smtp commands like BDAT?
2) how can one troubleshoot emails in queue if they have failed ?
3) I was told dynamic distribution gropus depend on oauth module? what is that
4) what is relation between exchange and Active Directory? I told ADtopology is needed for mail flow
also all user attributes for exchange are taken from AD. I was told not good answer?