I was just noting how much I love it, and that I really need to polish up and publish my mail system.

Test mail from myself is literally 12 (11+envelope) headers.

(Envelope) From, Return-Path, a single Received, Date, From, To, Subject, Message-ID, MIME-Version, Content-Type, Content-Disposition, and User-Agent.

Only the first 3 actually come from the transport, and half of the rest are optional stuff the MUA put there.

And the whole thing was end-to-end encrypted.