We should stick stamps on emails just because it's cute.
@bleeptrack client seems like a good place, maybe mailservers can be allowed to add to the stamp. Would this be a generative thing based on string(s) in the header? That would be cool, like the 'received' header, it can be multiple and each adds to it. Hmm, could also use the 'received' header as a stamp modifier.
sending client inserts initial stamp string, receiving client generates stamp based on initial stamp string + all 'received' headers.
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.