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:
and
https://mecsa.jrc.ec.europa.eu/ (offline atm Azure??)
Getting a clean ip is hard. I have my personal email server setup and had to get it off of some black lists maintained by baracuda. Although i agree personal self hosted email is fairly straightforward and ideally more people should do it. Hetzner provides cheap and reliable vms.
loading story #50483165
>Hetzner provides cheap and reliable vms.
True, i have some hetzner (not vm's but metal), and Vultr (just vm's), i just had one bad IP until now (i just changed it instead of trying to get it removed from a blacklist)