A user gets sent an email that has CC'd addresses in it. If the user
"reply's to all", the CC'd addresses are amended so that their domain
is changed to the domain of the original sender.

I.e., email come in from me@you.com. There are 2 CC'd addresses,
Him@them.com and her@those.com. When reply to all is clicked, the CC'd
addresses are changed from them.com and those.com to you.com.

The user then gets an undeliverable message as the amended addresses
don't exist.

The emails having the problem are going through a groupwise connector
onto an Exchange 2003 box. Could it be the connector?

Has anybody seen this before?