There's also mailcow that's popular in the self hosting crowd. Anyone use it and can share experience ? I'm a bit lazy to switch email since the other end of the mail is going to be gmail/outlook etc. anyway. So not much net gain.
I'm running mailcow for about a year now. So far so good, very little to no maintenance and the update process through the dockerized version is very easy. Using it with a few friends and 10 custom domains with wildcard addresses, no issues with the spam-filter either.
I'm only slightly worried if they ever abandon the project I'm out of luck maintaining it by myself. But since it's all based on standard software it's rather easy so switch to another solution I guess.
IMAP idle doesn't really work on mobile devices anymore, because no recent version of Android or iOS allows apps to keep the radio alive with persistent TCP connections - you need something that supports APNS and GCM, converting every notification into an HTTP Post request to Apple or Google or another notification provider.
So far, there seems to be no standard extension to IMAP to integrate with those, so you need some app which has a server side component to do it. (Which is exactly what Gmail, Outlook, Whatsapp, Facebook Messenger, etc. all do).
k-9 works fine for me without gcm. So at least on latest aosp, it appears that imap idle is all that it needs. Also, signal, whatsapp and telegram work without gcm as well.
Edit: I don't remember if I had to whitelist k-9 under battery optimisations. Maybe that's a requirement to use notifications without gcm, as it's a common theme in all apps that support notifications without gcm. On Apple devices, you will be generally out of luck, but that's a foregone conclusion.
Great addition, from a quick trial I can say the admin interface is easy to use and has all settings you need as a manager of multiple users and domains.
