> Has anyone ever used / configured Exim as an email server to receive
> incoming e-mails, capture an attached file and then save the file off
> somewhere in a directory?
I recommend MailScanner [1] which, apart from a number of other useful
tasks, has done that for me in the past. It's rather easy to integrate
with Exim and documentation is pretty good.
Otherwise a transport to a pipe with a custom made program ought to do
the trick.
-JP
[1]
http://www.mailscanner.info/