I don't disagree, but I do believe that the mailer should be smart enough to
(1) handle bi-directional transmission (not let long incoming files block
outgoing messages),
(2) allow you to preview the headers of "large" files so that you can
decide whether you want to transfer the whole thing or not,
(3) allow you to safely abort a transfer if it is inconvenient - note that
it MUST ALREADY be able to do this; there is always the possibility
that the link will fail or local disk will fill up.
None of these are particularly difficult to implement. You should demand them
of your mailer software.
It is also the case that email remains the only (nearly) ubiquitous mechanism
for sending data around. You and I are at locations that permit easy internet
access, but some many people are not so lucky. Quite a few companies make it
very difficult to impossible to access other internet services.
I agree that a mechanism could be set up to handle both submissions to and
from the "internet challenged", but I do not believe that is the right way to
go.
Bill