a) an accreditation process which would include certification of a legit
sender. The sender has to present himself/herself before a physical post
office for example.
Right. There's a bunch of possibile reputation systems here, from
ISIPP's IADB o the proposed .mail domain
b) a bulk stamp purchase agreement is executed and paid for by the
originator.
c) a set of designated relay servers would be designated to "affix the
stamp" on behalf of the originator, the bulk sender.
d) any relay could verify that a stamp instance as valid with a remote
lookup; forgeries would be thwarted because the stamp expires and other
characteristics.
You're conflating two unrelated things here. Authenticating senders is
a fine idea. That's what proposals such as SPF and Domain Keys do, with
no stamps needed.
E-postage is a horrible idea because it introduces more problems than
it is supposed to solve. See my white paper at http://www.taugh.com
for a longer discussion of the insoluble problems with e-postage.
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
http://www.taugh.com
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