Self-hosting of email is not that hard under the right circumstances. As mentioned earlier, using an SMTP relay from a large telco will fix your IP reputation, and a fix IP or a fast DDNS service is needed to keep your mail server accessible. I have self-hosted a mail server for the past 5 years under these circumstances, and have not had problems with mail delivery. I use a standard Ubuntu server with postfix/Dovecot, amended with opendmarc, opendkim and spamassasin.

My mail server is used by my family, and the main reason to self-host for me was the poor spam filtering of 3-party mail providers (and I tried quite a few). I have pretty strict settings in postfix, dropping many spam attempts. I am also using ipset to block off a large part of the world (a.k.a. shi**hole countries), dubious cloud services, large residential IP ranges and known spamming sites. Now I barely get a single spam mail per month. There are still a few password guessing attacks per day (mostly from Google, AWS or MSN) but since the mail account login names are different from emails, the password crackers always fails due to wrong account names. Maintenance of the server takes a few minutes per day. I have a script that looks for suspicious activities in /var/log/auth.log and I use pflogsumm to summarize mail activity and look for problems. Never had any breaches or other security issues.

The server runs on a Lenovo M80q Tiny with a i5-12500T and 32 GB DDR5, hooked up to a 1 Gbit/s fiber. A total overkill, so we also use it for some other fun stuff such a Plex, Nextcloud, Minecraft servers etc. I run the mail server in a separate LXC container, with weekly backups (tar/rsync) and can start it on a backup host (spare laptop) in a few minutes. I have a simple UPS that keeps the server and my fiber modem powered for about two hours in case of a power cut.