I don't buy into the myth that running your own mail server is "hard".
For a server with only a few users, the hard part is outgoing mail, ensuring your mails get delivered. I did what I can here, and simply use a paid service on another domain for important things where delivery must be "guaranteed".
It's an interesting post, but saying it's "not hard" and then "welllllll it's not hard if you don't bother with a spam filter & pay a professional company for 'important' email" is pretty misleading.
It's also not true. I ran an own mail server for a few years. If you're strict with the protocols it actually isn't a hard thing. Even setting up spam filtering isn't really complicated. Everything has to be done once. Maintenance really isn't problematic. Just keep an eye on the monitoring if something crazy is happening and regularly do updates and check your certificates.
For a server with only a few users, the hard part is outgoing mail, ensuring your mails get delivered.
It is not particularly difficult from a technical point of view.
But if you get blocked by big tech even when doing everything right (reverse DNS, SPF, DMARC, DKIM, RFC compliant MTA),
you have to beg them to unblock you. This part is time consuming.
I've read horror stories where it went well for years until suddenly Gmail started flagging well-behaved servers as spam without any clear reason. Sometimes mail got through, sometimes it didn't, without any clear pattern or explanation.
I simply don't have that kind of time and nerves to deal with this. "hard" may be the wrong word, but it is nerve-wrecking.
That's why I finally gave up after nearly 3 decades of running my own email server. It's just stamping out fire after fire and my time became way more valuable as I got older.