If you have OWA available perhaps:

  http://code.google.com/p/weboutlook/

could work?

Also what OS are you running roundup on? If you are on windows
and have outlook available I think there is a COM interface to
MAPI that may be usable.

Google for python and these these terms. There are a ton of hits.

In theory it should be possible to send and retrieve email this way,
but AFAIK nobody has done the development to make this work with
roundup. Also given that it's proprietary and poorly documented
and keeps changing with different exchange versions, it's a hard
way to do it.

If you are running on linux, have the exchange people
forward the email though the exchange server to your internal
server and handle the mail there.