SBS Exchange Problem

Hi
Please help me…..My company is using a external pop3 account for email…and also have web mail for that accounts…now i install a sbs exchange server and configure it to receive the pop3 mail through pop3 connector and routed to users inbox….my company email domain is xyzexternal.com and my internal domain name is xyz.local…

My problem is that when a user send a mail to another users external pop3 email (user@xyzexternal.com),it receive in the local inbox(user@xyz.local) not in the external pop3 mail(user@xyzexternal.com)…so the traveling
users are not able to receive mails in web mail when they out of office…

Thanks In Advance