If we accept that some form of store and forward intermediary is possible
(I'm not entirely convinced it's within the scope that we've been
considering, but I'll go with the consensus) without necessarily discussing
how the solution would work, it does bring up the issue of authentication
between sender and recipient (the analog of the CSID string, time and date)
and who gets notifications and when, so it's a good point to bring up.
I think IPP could handle being the protocol for this sort of dial-up
connection, but it wouldn't be an efficient way to do it. IPP is initiated
by the client end rather than requested by the server, so any document
store would have to act as an IPP client to transfer the stored document to
its ultimate destination. However, the only mechanism I'm aware of to
handle this store-and-forward functionality is repeatedly polling the
server to see if it's up (that could be as simple as ICMP echoes, but it's
still ugly).
Then again, an ISP could implement a QualDocs repository which would be the
document store you describe, with the dial up server using some other
protocol (maybe SMTP) to get the job. I guess that's the same as the SMTP
gateway I mentioned in an earlier post on the subject.
Cheers,
Nick Webb