I use them as well, they have custom domain and two factor authentification support. The only complain is that sharing in their online Office can be buggy, i ho

I use them as well, they have custom domain and two factor authentification support. The only complain is that sharing in their online Office can be buggy, i hope Open-Xchange will fix that, but that's more of a side feature for me. At least their business model seems more honest than Proton Mail.