SMTP Help: Can’t receive email on Exchange 2007

Hi everyone
i’m new to Exchange 2007 and i’m needing help getting it to accept emails from the internet. I can send and receive internally. I can telnet port 25 and get the banner internally. I can send email to the internet. I have OWA setup and running Ok internally and externally. I just can’t receive emails send from the internet.

I have only one machine available and i wanted to test Exchange 2007 before going to the real office environemnt. So i’ve set it as DC and the installation has run smooth. I installed all the Exchange Roles except the Edge Transport, obviously. The domain is shoppingmadeira.com and the server is exchange.shoppingmadeira.com. I have also enabled port 25 on the router, forwarding it to the internal IP. On the DNS Management i created an A record “mail” pointing to the external IP of the router and an MX record pointing to the A record. The same was done on the domain.

The messages sent from the internet are bounced with the following error:
For , Gave up after 12 hours, last error: open (n.n.n.n) 23s failed A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

What should i do to get this right?

Thanks
Carla