I ran a miab for about 5 years, maybe around 2018, I also actively tried to do extra things that would improve delivery, including registering postmaster accounts on the various postmaster whitelist tools etc in order to increase the chances my mail would be delivered.

Unfortunately if you host your mail on linode/digital ocean, you will eventually be blocked, and mst of your email will end up in spam folders.

This year after 13 years of running my own mail services, I finally gave up, I was sending emails and then sending followup “did you get my email” messages from gmail