I'm been running a mail server on my personal domain for 20 years. The hosting provider is key. One well-known hosting provider I used to use had lots of IPs

I'm been running a mail server on my personal domain for 20 years. The hosting provider is key. One well-known hosting provider I used to use had lots of IPs on the e-mail blacklists. I found a slightly less well-known provider without this problem. I test sending and receiving to Gmail accounts and Microsoft 365(?) accounts, and they all seem to work fine if I just configure reverse DNS, ipv6, and TLS (certificates from Let's Encrypt) correctly. I use Postfix. When I e-mail bomb (40 emails or so) from a Moodle server, sometimes emails show up in spam folders on Microsoft servers, but that's the worst of it.