I've been using Soverin for almost two years now https://soverin.net/. I chose them because of the their privacy focus and the fact that at the time I was looking for a bare-bones email service.

For the most part it works well, the only (rare) problem I've had was with Soverin rejecting emails from my Google forwarding rule. I've encountered ~10 instances of this error in nearly two years so I'm not that concerned about it.

They use RoundCube for the web interface, which I don't use. I prefer Thunderbird on the desktop and use the Gmail app on my phone.