I took mailbox because i thought @mailbox.org looked professional, atleast better than something like @tutamail.com They market themselves as privacy concious but they aren't, really. It has support for PGP and all, but the whole thing is just a wrapper around the Open-Xchange standard, and a barebones wrapper at that. Development happens at a snails pace, meaning it has fallen behind most of its competitors. The 2FA implementation is partial at best, the "Open Sessions" page which is supposed to list and allow you to log out of connected sessions only lists browser based sessions - not connections via IMAP with other software meaning using open source programs like thunderbird won't show up on the open sessions page.

You can check the mailbox forums for a long list of threads where users air their grievances at an at-best understaffed, at-worst indifferent, staff.