How does the post office do it? It receives mail from other countries
and determines what kind of stamps official franking etc to either
deliver or return to sender unopened.
International postal mail is one of the worst possible analogies for
Internet mail. It's a closed system consisting of only 190 post offices,
each of which is a national monopoly. All the security is at the
perimeter, i.e., when you mail a letter to England, the USPS checks that
the stamp is real, but when the USPS hands it to RM, RM assumes it's OK.
There's a complex settlement scheme to share postage revenue when the
bilateral flow of mail is unbalanced which has no online equivalent, thank
goodness.
And, of course, there's no identity security at all on postal mail. I can
write "Bill Oxley" as the return address on a letter, mail it, and no post
office will notice or care.
Although it is completely irrelevant to Internet mail, the international
postal system, which goes back to the 1870s, and its history are quite
interesting. See http://www.upu.int.
DKIM is an electronic stamp, SSP (to me) appears to be the franking
system.
This is so wrong I don't know where to start.
R's,
John
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