Thank you, this is essential!

Reading mox FAQ, it looks close enough to the ideal: https://www.xmox.nl/faq/#hdr-how-do-i-stay-up-to-date

I'm currently running a more classic setup with postfix and dovecot, because the updates and security fixes are managed by Debian. Once things are configured, I don't need to do anything using unattended upgrades (other than upgrade Debian itself when the LTS version goes out of support, that is!).

At this point it is easier for me to not touch what I have, but in my next mail server I will consider mox!