I’ve honestly been thinking that the replacement for Z-Push is SoGO Groupware - https://www.sogo.nu/
Seems there was a folk for MiaB a while ago (GitHub - jkaberg/mailinabox-sogo: Mail-in-a-Box helps individuals take back control of their email by defining a one-click, easy-to-deploy SMTP+everything else server: a mail server in a box.) but is no longer maintained since it appears it was from the Ubuntu 16.04 era. too bad honestly.
Was also some mention of it back in 2018, but I dont think it went anywhere. (SOGo for mail, contact, and calendars)
Maybe with Z-Push sorta being not supported something like this could be considered again but my fear is that Z-Push will just be dropped from MiaB.
Maybe @JoshData could chime in here. Ultimately I don’t think there are enough developers on this project to sorta even maintain what we have yet alone add something. I’m very grateful for the project but having a hard time understanding where this fits in with my long term strategy to host my own mail. Many of us rely on the project to be updated and probably only a few of us rely on Z-Push. Josh, don’t want to press you for an answer because I’m afraid I already know will happen.
Thanks (and sorry)