Exchange Meeting Request to External E-mail

I don’t know if this is our Exchange Server doing this or another
problem. Internal meeting requests to users on the network show up
just fine. PC to PC is just fine. Intermittantly the Macs will fail with
the below example.

I am finding, however that Macs and PC’s outside the network
(sending a meeting request to, say, another company’s e-mail) the
meeting request will come through like this:

——
When: Thursday, March 01, 2007 3:00 PM-4:00 PM (GMT-05:00)
Eastern Time (US & Canada).
Where: This is a test

*~*~*~*~*~*~*~*~*~*

test
——

We have the latest Mac Entourage, PC Outlook and Exchange Server
updates installed on our servers. I don’t know what is causing this.
Anyone know?