The stamps on a received mail should get semi-transparant post marks for each hop from the respective server. Could be generated from the mail header info.
But serious question: where would I "inject" my stamp generation on the mail process? Would need to be a client plugin or something like that, I guess?
@bleeptrack my Claws mail client displays faces when they are in the header X-Face... it's just that folks usually have *one* face configured... you could generate a new one for every mail, and everyone who has X-Face configured would see them