The case for running your own mail server

Everyone tells you not to run your own mail server. I have been running mine for four years and I am here to tell you that everyone is roughly half right, which is the most annoying kind of right.

What actually breaks

Not what you expect. It is never the SMTP daemon. It is DNS records you set up once and never looked at again, a certificate you renewed by hand in a hurry, and the slow, invisible business of your IP address acquiring a reputation you did not ask for.

dig +short MX example.com
dig +short TXT example.com    # SPF
openssl s_client -starttls smtp -connect mail.example.com:587

Run those three every few months and you will catch most of it before someone tells you their reply bounced.

The part I underestimated

Deliverability is not a technical problem, it is a political one, and you are a very small country. The large providers are not obliged to explain themselves to you and generally will not.

I still think it is worth doing, for the same reason I still think it is worth owning the domain your email arrives at. But do it with a second address somewhere else, and do not find out about an outage from your mother.