Has anyone on this list got hands-on experience with Stalwart email server software? https://stalw.art/ It's an entire email stack written in Rust. Replaces Postfix, Dovecot, OpenDKIM, fail-2-ban, Mailman (has a built-in mailing list, no need for the nightmare that is MM anymore), supports CalDAV, CardDAV, WebDAV, JMAP, IMAP, POP3, anti-spam, Sieve, etc. Web site's really fast, even the management console run from inside a Docker container is fast, well designed, well laid out. It's appealing to shed the 1,000+ options for Postfix, even more for Dovecot, plus all the ancillary tools required to run email. On the other hand, Postfix & Dovecot are what I know - and learned at great cost (time & frustration), and are where the jobs are. What brought me to this is, looking for a way to offer contacts & calendar syncing along with email hosting. NextCloud was my first choice, but trying to get the AIO (All In One) to support multiple domains in one instance is not well supported as best I can tell.