Exim and Dovecot virtual domains, users
Can you recommend a modern guide on setting up Exim and Dovecot with virtual domains and users on Debian (or Ubuntu)?
As I have never used Exim before, I did some research on it and I found that it is possible to set it up on a Debian or Ubuntu distribution. It can be used in place of Sendmail, although according to what I've found they have very different configurations.
Ubuntu has a guide for setting up Exim on Ubuntu 18.04, and you can find that here:
According to Exim's page, all of its releases prior to version 4.93 are now obsolete.
Since Exim is a Mail Transfer Agent, it can be used in place of another, like Sendmail or Postfix. To test this out, I went through our guide for installing Postfix/Dovecot/MySQL on a Linode (using Debian). While going through the guide, I left out all references to Postfix and installed Exim4 via the Debian guide linked above instead. It looks to have been successful. For reference, here is our guide that I used:
As for virtual hosts and users, you should just be able to go about that the normal way using MySQL:
I hope this gives you some guidance. A lot of this was just me experimenting because what I found online were all older guides (like I assume you did as well). I'd be interested in getting an update here from you on any successes you have with this.