I have my Sendmail configured to cut off anything past 256 KB in the
collect phase. At first I had it configured to reject the whole message
(close the SMTP connection while the junk is still spewing), but people
started assuming that my E-mail address was bad instead of realizing
that they were sending oversize junk, so I've changed it to cut off and
discard the excess fat, but still let the first 256 KB through so I at
least see that someone tried to send me something.
Files are meant to be FTPed, not E-mailed. If someone is too stupid to
use a real command line FTP client to upload a file to my FTP drop box,
I make them use www.yousendit.com.
At Creighton the VP for IT explained to me that the President of the
University was too stupid to use FTP.
So we had to rebuild the mail system to send his Power Point
Presentation the 150 yards to the President's Office. (I don't remember
how big it was--a two-hour presentation as I recall.)
I think its generally agreed that FTP is used for file transfers,
but unfortunately the option exists to attach files within an email thanks
in part to MS/AOL/Compuserve and numerous others long ago. I believe its due
in part to ease of use for those that aren't technically inclined to know
better, and make things "easier" for them (harder on others).
Kind of like cattle, if you leave a hole (or make a hole) in the fence
eventually it will be used and the only thing you can do is build a fence
outside of the hole to keep the heard from getting to far.