I've noticed some wierd problems with my Outlook 2003 client. It
intermittently sends email intended for an internal user outside of our
organization through our exchange 2000 server. If sending to a Distribution
list created on the exchange server, and the email happens to go out to the
internet first, the message comes back to the sender as shown below. Any
thoughts on this? We never had the problem with Outlook 2000 only 2003.

Subject: Undelivered Mail Returned to Sender

This is the Postfix program at host relay02.roc.ny.frontiernet.net.

I'm sorry to have to inform you that your message could not be delivered to
one or more recipients. It's attached below.

For further assistance, please send mail to postmaster

If you do so, please include this problem report. You can delete your own
text from the attached returned message.

The Postfix program

: host
rrlhcflt0201.lhc.redrivernet.com[66.185.224.7] said: 550 5.1.1
... User unknown (in reply to
RCPT TO command)