We have a problem where some VPN clients are not able to access the server and receive the 721 error message. This is only occuring when the clients are using specific wireless or wired networks. I believe the host network is not allowing the standard PPTP connections. Is there another way I can open up to allow these connections safely. We are using Windows 2000 Server, ISA Server 2000, and Windows XP clients. These clients can connect in most cases.