Exim VS Dovecot

Documentation for ARC is pretty sparse.

The instructions for setting it up in Exim (default MTA on Debian systems) can be found here: https://github.com/Exim/exim/blob/master/doc/doc-txt/experim...

(AFAICT, there is absolutely no mention of ARC in the main Exim documentation: https://exim.org/docs.html)

Exim:​​​​​https://www.exim.org/

EXIM is a popular option, though it seems to be subject to just as many vulnerabilities and exploits as exchange is.. so either way you go make sure to patch regularly

Run your own. Usually with Exim or Postfix.

I can either direct particular addresses to a mailbox on the VPS where they can be retrieved with POP3, or can forward them to any arbitrary address. Or anything else I can configure exim to do.

I use Exim

Mail server using Postfix, Dovecot, and Rspamd

Eventually I will set up Dovecot as a local IMAP server, pointing to that Maildir. When I've done this before, I've set up a self-signed certificate so Apple Mail wouldn't complain.

You might want to use dovecot for this if I understandyou correctly

If you really want to try it (and keep it up to date for security fixes, check and handle any relay issues or possible spam attackers) then look at Dovecot or Kerio

An IMAP server. I have a strong preference for dovecot for this.

I'd do it with a local IMAP server in conjunction with a webmail client that connects to it. Dovecot is a fantastic and easy to use IMAP server. Webmail clients are a pretty personal thing, but the last time I used Roundcube it seemed pretty good.

For the record, I'm using dovecot (https://www.dovecot.org/) for IMAP and Haraka (https://haraka.github.io/) for SMTP.

self hosting mail is always a pain and can take up a lot of support time and you really need to know your stuff. I always use Plesk witch configures Dovecot. But if there is anyway you can push them to use an external service you should do that.

I run a mail server on DigitalOcean for a few domains using a fairly standard FreeBSD setup running dovecot and postfix. If you're set up your preferred stack on another hosting provider before, you're aware of all the pitfalls: