binbag

binbag scores every message in an IMAP mailbox, Gmail, iCloud, Outlook and the rest, from its headers alone, then shows each sender with what it plans to do and why before anything moves. Junk goes to your Bin, never deleted, and receipts, bookings, security codes and anyone you've emailed are protected whatever the score.

There is exactly one place in the code that changes a mailbox, and the tests fail if a second appears. It never sends the IMAP command that silently erases mail, never downloads message contents, and its local web page refuses requests from any other site.