Re: POP3 "resume download" extension

fwiw, a lot of folks are likely to push back on defining any new extension
to pop.  there is a feeling that two mail access protocols are too many,
and that new effort should be invested into imap rather than pop.
but that doesn't mean you shouldn't try, just be aware that you may get
some pushback, perhaps enough that it doesn't fly.

if you do define an extension for partial message retrieval I think it 
should allow partial message retrieval (e.g. byte count) rather than 
just resume.  that way, you don't have to drop a connection to 
get the server to stop sending you a message.  I also suspect it should 
be a different command rather than an extension to RETR - with the latter 
approach my guess is you're likely to run into some compatibility problems 
with old servers.   

but something like 

PRET <msgno> <start> <max-length>

(PRET = "partial retrieve")

where <start> is not a byte offset but a cookie that is returned
from a previous PRET command (if you want to resume here, use this cookie
in the next PRET command)...that would allow for different back-end 
representations.  only problem is it doesn't work well for pipelining -
you can't send request #N until  you've received response #N-1 -
but maybe someone will think of something.

Keith