I've heard many people say good things about Fastmail, and I'm sure its worth the praise it gets. But I personally don't recommend it because it gets very expensive if you need more than a couple of mailboxes. The services I listed, at least Posteo and Mailbox, are significantly cheaper for those who need separate mailboxes (not aliases on a single account). I moved from Gmail/Yahoo more than a year ago for just two of my primary mailboxes (one personal and one shared) and it costs me a fraction of what a single mailbox on Fastmail would.