That’s right. Also important, email is not a playground for experiments. Once it runs, you should not touch it anymore, except for updates. Otherwise, you will do harm to your own way of communicating. One error, and you will lose all your reputation and someone spams half of the internet with your domain as sender.
An when it runs, the only thing to improve is tuning the spam-filter for your instance. Implementing all the rules that you fight the other day, because otherwise your inbox explodes. So you have to do all the shady things and block ips, filter with blacklists and check every dns for all those extra entries, needed for delivering mail… You must become a part of the problem, spammers all behind every cracked wordpress and insecure vps out there.
That’s not true. I run my own email server for 15+ years now. There are only 5 of 6 mailboxes. I never had a problem with any other host. Not Microsoft, not Google. Maybe, the reason was, the IP was also 15+ years assigned to the same domain. I have only known senders, family and friends.
The last days, the hole subnet was blacklisted on some blacklists. So that was not my fault, the growing business of the provider lead to this situation. Eventually I moved to a very small provider and run a mail cow on a vps. On a fresh IP without any reputation. Same ‘customers’, the only issue was with T-Online in Germany, but a mail solved this. To keep this kind of issues away, I use sendgrid as a SMTP forward. With only a few mails per day, this is free. Mailcow provides a lot of features, rspam filtering, a lot better and faster than spamassin. Active sync, imap, webmail, everything. Solid backup, runs without any problem.