So you have sold SBS and Windows Mobile, but your customer gets a problem - how do you diagnose it and fix it - have a look at the ActiveSync 4.x Troubleshooting Guide - Firewall, VPN and Proxy . It contains the following sections: Installation Initial Configuration USB Issues Guest Issues Firewall and Proxy Issues Outlook Errors Synchronization Errors Mobile Information Server / Outlook Mobile Access Exchange ActiveSync Error Codes and Solutions Missing Calendar, Contacts or Tasks Items Security Advisories ActiveSync 4.x Troubleshooting Guide - General ActiveSync 4.x Troubleshooting Guide - Limitations ActiveSync 4.x Troubleshooting Guide - 85010014 ActiveSync 4.x Troubleshooting Guide - Firewall, VPN, Proxy ActiveSync 4.x Troubleshooting Guide - Logs & Services ActiveSync 4.x Troubleshooting Guide - Connection Flow USB Advanced Network Functionality Microsoft ActiveSync 4.2 Troubleshooting Using ActiveSync 4.x and Visual Studio 2005 and the Emulator Understanding ActiveSync or WMDC Partnerships ttfn David...