I self-host a "traditional" mail stack using LXD containers. Webmail is Roundcube in one container, mail spool is Dovecot in another container (and the spool is

I self-host a "traditional" mail stack using LXD containers. Webmail is Roundcube in one container, mail spool is Dovecot in another container (and the spool is actually independent of the container, and mounted inside), mail exchange is Postfix in a third container doing LMTP to the Dovecot container (and also has an independent mount for the temp spooling of email). The Dovecot instance has Sieve available to it, and Roundcube has the sieve plugin installed and able to write server-side rules for filtering. Address book is stored in a DB, and exposed via nextcloud's carddav. Works in KMail, iOS mail, Thunderbird. I dunno if you can consider Roundcube to be modern, but all I want from a mail client is the ability to read and compose email, so it works for my needs.