I have an exchange server 2003, everything was working just fine and there was no change since last few weeks.
But suddenly nobody can't send email to external (yahoo,gmail..etc). We can only recieve email from external (yahoo,gmail...etc).
We can only send and recieve email from people who is in our domain only.
Here is the general map of my network:
exchange --switch--firewall--public internet
What do I have to do to trouble shoot this problem?