Eliot Lear wrote:
there was something of a view that the whole point of
MXes was for the MX relay to bridge between online and offline devices.
It was well understood at the time that MANY more systems were in fact
on the networks that you mentioned than were on the ARPANET. And I
would even argue that there MXes solved a major problem, which was that
there was that sites that sat on both UUCP and the Internet often times
Got It Wrong with regard to the precedence of "!". The abstraction that
MX provided made relaying behavior much more explicit. I think this was
understood at the time.
UUCP, Bitnet, CSNet, oh and let's not forget Arpanet-to-Internet transition
(FTP to SMTP mail)...
Administrative boundaries are not just bookkeeping constructs. They can have
fundamentla technical impact. Take, for example, exterior routing technology
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