[pixelHD]

I've used mailcow before. It's a pleasure to use and comes with a decent-ish material design mail client as well.

[whalesalad]

Yikes. Any time I hear material design and associate it with an open source project I know the UI is going to be a nightmare.

[benji_is_me]

Just setup mailcow. Not bad at all to setup. It uses SOGo for the web client.