Microsoft exchange server 2003

hi this is my first post in techrepublic and i hope i find my solution here.
the problem is we set up a new ‘vigor2800’ router in our networkd internet is working fine but now we cant send and receive email from out side as we are using exchange server.
we can send and recive emails inside of our firm but we cant receive and send emails from outside.also we are on static ip address.plz help me.
and tell me in detail what is the problem and how to solve this proble.
thx
regards
Umar