I have a user that sets up recurring meetings with outside contractors. These
go out to 3 external mail domains. The first time he sets up the meetings,
the outside contractors get the meetings and accept them, but when the user
sends an update to these outside users, the messages get stuck in the
exchange queue and are never received. Even forcing a connection doesn't do
anything.

We are using Outlook 2007 running on XP sp3, with an Exchange 2003 server.
Could any third party program on the users laptop affect this?

Thanks