Question : Problems accessing Webmail from external computers

Hi Experts,
I have a server running as DC and Exchange Server, so far all is good except for accessing email from the Webmail function of exchange server, i can access webmail if i am inside the network and by using the internal IP address to the exchange server but if i try to use the external IP address and the mail.domainname.com/exchange doesn't work at all. i had exchange installed on this server before and the access from both was ok, i had to reinstalled everything again because SBS needed to be the primary DC, etc..
installing everything again was paintfull but is working except for this detail, can you think of something to do?
i have a snapgear router and all port ready and allowing to get exchange.
thanks

Answer : Problems accessing Webmail from external computers

have you check whether the firewall is turn on ?
2nd thing you might want to check whether your IIS allow outside

check on the default web site properties/directory security
on ip address and domain name restriction click edit

check whether is there anything there.