Contrary to popular opinion, I don't think the technical aspects of operating a mail server are all that hard. Perhaps I'm underestimating the learning curve since I've been doing it for 27 years. (If you're running your own mail server, you are the sysadmin.)

The frustration comes with scenarios such as the one outlined in this blog post, where small mail server operators get bullied even though they are doing everything right. I can completely understand not wanting to operate a mail server due to this situation, or not having interest in leveling-up server administration skills.

For those of us who do have expertise in running mail servers, it's a shame we have to deal with these obstacles.

The biggest obstacle of course is dealing with deliverability problems. As most posters have commented here, getting people to accept your mail, and accepting mail from reputable sources isn't an easy problem to solve. At FastMail, a considerable amount of time is spent ensuring customers don't need to worry about deliverability problems or spammy inboxes.

To me, that's the biggest reason not to spend time running your own infrastructure for mail. Getting people to accept your mail reliably, is much harder than adjusting some postfix configuration.

Because email is one of the few edifices left of the truly open internet, and some of us aren’t ready to concede defeat of what was once a free platform to a corporate oligarchy.

If you've been doing it for 15 years, why should you have to stop?

It's not as difficult as you've been lead to believe. But if you have no experience with administering servers, the initial learning curve could be significant.

The upsides, sharing many of the common features of all self-hosting, are things such as pure and total control, data privacy, ultimate flexibility of configuration (e.g., infinite and unfettered aliasing), customization of interface, high-performance, etc.

Because they have no way of measuring how much of their outbound mail is going straight to Junk, so they just assume their messages are being ignored.