The problem is: When a meeting request is sent from the internet, we do not see it at all. No meeting request, no email, nothing. I have confirmed it is making past the Barracuda spam filter and being forward by our Interscan email viruswall. All internal meeting requests are functioning fine. I have prevented the spam filter and the virus scanner from modifiying the email headers. I also turned the virus scanner completely off and still had the same result. Any ideas? We're using Exchange 07 sp1 and my email client is Outlook 2007.