@Hyolobrika Doable but difficult:

- Make sure server host / ISP doesn't block ports.
- Request IP to be removed from blacklists if it is on some due to IP having previously been abused.
- Request some mail providers specifically whitelist it because they have their own whitelists/blacklists.
- Make sure to implement SPF, DMARC, and DKIM.
- Make sure you don't accidentally set it up as an open relay.
- Make sure PTR records are set correctly for rDNS.

I may have forgotten some steps lol. The FeministWiki has a mail server that seems to be working quite well, but still occasionally runs into issues.