User forwards duplicate e-mails

I have a laptop user on XP Pro using Outlook 2002. We are using Borderware firewall/Mail Server 6.0.2 and Exchange 2000 behind the firewall. His account is set-up to send and receive through Exchange and receive only through Borderware. He also syncs an Ipaq with Outlook. Sending mail to external distribution lists delivers only one copy but forwarding a message to a distribution list delivers 2 messages to each recipient. No duplicates to internal lists. We have around 100 users and he isthe only one experiencing this. I have removed his account from active directory and rebuilt his system.