Server isExchange 2007 sp1 running on Windows 2003 R2 x64. All clients are Windows XP SP3, running Outlook 2007 connected directly to exchange (some are in Cached mode, some not). The outlook clients are of various builds/SP levels.We have OWA, however we never had a good certificate to put on the exchange server. I finally purchased a Certificate two weeks ago, and OWA no longer gets the certificate warning in IE. Since that change however, all clientsare getting a certificate error on his outlook! No matter how many times I say "YES" to the prompt, it will always return the next time outlooks starts.The prompt comes up, I hit yes, and 1 second later it comes up again, I hit yes, then it stays gone until I restart outlook.the Certificate is signed to site name webmail.domain.com, while the server name is of course exserver.domain.com. https://webmail.domain.com/owa is how we access our OWA. The certificate in IIS is installed on the default website.. should it only be installed on the owa sub-website? What else can I try?

My original post stated the problem was limited to VPN clients, but after letting it sit for a few days, Everyone in the organization is getting this warning from outlook. I updated the original post with this new info.