Mail servers are easy, getting the other mail servers (Microsoft,Gmail,etc) to play nice with yours is harder.
Not that hard, for example thats a good tester:
https://mail-tester.com/
and
https://mecsa.jrc.ec.europa.eu/ (offline atm Azure??)
alt Hacker News
Not that hard, for example thats a good tester:
https://mail-tester.com/
and
https://mecsa.jrc.ec.europa.eu/ (offline atm Azure??)