For me, the genius of Mailbox was twofold. First, using it simply felt faster than any email app I ever used. It pre-fetched messages in the background; whenever you opened it you could start dealing with the daily horror of your inbox right away. Second, using it was satisfying in a way no other email client was: every time I swiped my fat thumb on a message, banishing it to the archive, the email turned a lustrous green. Mailbox was good for dashing off quick replies, but it was best-in-class for cleaning house. Every time I found myself standing in a line, I’d open up Mailbox and positively murder my inbox. Mailbox turned you into an email assassin.