http://www.microsoft.com/exchange/techinfo/mobile/
Chapter 6, "Managing Client Access to Exchange Server" in the Exchange Server 2003 Administration Guide
Chapter 8, "Configuring Exchange Server 2003 for Client Access" in the Exchange Server 2003 Deployment Guide
Configuring Mobile Devices to connect to Exchange Server 2003
www.msexchange.org/tutorials/Configuring-Mobile-Devices-Exchange2003.html
Outlook Mobile Access (OMA) in Exchange Server 2003
www.msexchange.org/tutorials/OMA_Exchange_Server_2003.html
Exchange Server 2003 Client Access Guide
http://www.microsoft.com/technet/prodtechnol/Exchange/guides/E2k3ClientAccGuide/7ff636d5-a97d-4ac9-a090-10eb428ccf83.mspx
Mobility in the Microsoft Exchange Team Blog
Known Issues:
Exchange ActiveSync and Outlook Mobile Access errors occur when SSL or forms-based authentication is required for Exchange Server 2003
http://support.microsoft.com/kb/817379/en-us
http://support.microsoft.com/?kbid=886346