This is driving me mad.
A friend of mine has recently been ill advised by an ISP support to reset his router. I say this because he is running a business with Exchange Server and the router should have been configured appropiately. Since this reset he has not been able to get on to the Inet until I talked him through setting up the router ip within his network. Now he is able to access the internet and is able to retreive emails BUT he cannot send emails. I suspect that there is some sort of outbound rule that needs to be applied to the router but cannot for the **** find how to do it. Neither Netopia or the ISP have been helpful in resolving the matter. He can send emails internally though. I don't suspect there is any issue with the Exchange server since no change has been made to it. The router is a Netopia 2247 nwg. PLEASE PLEASE Any help greatfully apppreciated!
I doubt the router has an outbound firewall blocking traffic.
Port 25 is outgoing mail (default) so you'll need to investigate why that's being blocked.
Is he assigned a static IP via his ISP? Most residential IPs have port 25 blocked unless you are sending mail through the ISPs mail system. Since he's sending mail on his own server, he'll need to make sure that the ISP has his IP in a 'business' group so that port 25 isn't blocked.
Since you can send/receive mail internally, then yes, most likely the Exchange server is fine.