Recently, there has been a lot of talk in my blog bubble about email self-hosting again (here is one example, here is a second one). I myself switched to a self-hosted mail server over a year ago, only to switch back to a hosted version a few months later.
For me there were no technical problems running Mailcow, I was even quite happy with my setup. Nevertheless I switched because I realized that email is a topic where it’s not really worth hosting it myself.
I migrated from a self-hosted mailcow-dockerized to the hosted version of Mailcow. It’s just because I don’t want to care about keeping everything up-to-date, secure and backup-ed. Now I have some stricter limits, but in the past I didn’t reach that limits and I doubt I will reach them ever. To migrate all emails, I used the online version of imapsync.
To answer the question why I didn’t migrate back to Fastmail (which I used previously): With Mailcow I have the possibility to create up to 20 different mailboxes instead of just one.