A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.
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Self hosting mail server is one of the worst ideas. You need to have top notch security, always updating patches and on top of that somehow manage to get your mail not to go into spam folder. Google and Microsoft don't usually like self hosted emails.
If you still are going to go through with this, good luck! I'm going to check regularly how your path goes. Sadly I can't help you at all, just some wide words repeated by others.
I admin a debian mail server in my job and hands down it is the biggest pain in the rear. The more I learn about it, the more I realize we have huge unsolvable gaps in documentation, maintenance ability, and monitoring.
If you do only web and mail you could consider a web space instead of a VPS. For example Netcup.eu offers packets which include email, Ionos offers one mail account per user account too I think.
Also as you said self hosting emails is quite some pain because Gmail, Microsoft etc blacklist small mail servers rather quickly. Depending on your motivation you could also use Protonmail or mailbox.org as mail provider with your own domain.
Anyway, Debian is a solid choice due to long support times.