Currently using Stalwart after about a decade of using iRedMail. Stalwart’s setup was such a breeze; I let out an audible laugh/noise when the install completed in the blink of an eye and had all the DKIM, DMARC, SPF, etc. settings available for config.

Making some nice improvements with each release too, proper user management, etc. Definitely a fan. Looking forward to when they support CalDAV and CardDAV.

Looks like you may have made a decision already, but wanted to give Polaris a mention. Been using that on my home server, has a nice Web-UI and a mobile app on F-Droid as well.

https://github.com/agersant/polaris