Configuring Exchange Server 2003 behind ISA 2004

Dear all,

I have just configured my organization Exchange Server 2003 behind ISA Server 2004, everything is going well but users outside the organization (from remote location, internet) can not access their email accounts, because ISA 2004 is preventing the users access to their email boxes (accounts), kindly help me in this regard, i will be very thankful to you.

Abdul Basit