Hi, sorry if this is in the wrong forum but i dunno where i can get a quick reply. I have a friend who has a exchange server, all emails were working fine until his modem stopped working. So he attached a spare modem instead of the broken one. However, no mail settings were changed and everything was working yesterday, now today only the offices RECIEVING emails are causing a problem as they can't recieve any but they can send mail. I am guessing that this is a firewall issue. As the new modem may have automatically changed the firewall rule. I have no experiences with exchange servers. Can someone please guide me on where to look and where to get the correct settings, please?

I forgot to add that the DNS Server is pointing the a different Router addres. How do i change this and get the correct address?

Is this indeed a modem or router? My assumption is that its modem in router mode, your friend will need to access the device and configure a NAT rule for SMTP (25) to the the internal IP address of the Exchange Server. I would also NAT HTTPs (443) for Outlook Web Access and Outlook Anywhere.MVP Exchange Server

He's now using a Netopia Modem. The ISP said that the DNS setting were pointing to the old Netopia router address and not the correct address. To me this means that i have to access the Netopia router via 192.168.1.1 or 192.168.1.254. and change the address. How do i configure the NAT rule if that is the case and as you described? Also, how do i get the internal IP address that needs to be used? I want to be prepared as i go in and do it for him. If he has forgotten his Netopia username and password, what other options do i have? Change the DNS settings on every computer to use opendns settings (that would be a tempory solution - i think).

Netopia website will be your friend in viewing a user manual for the model that is installed, it will explain how access the router with default admin and password. I will also explain how to create PAT rules per my previous post. As for DNS, if the Netopia is acting as the DHCP Server then that should be sufficient to allow devices behind the netopia to access internet. If the Netopia Public IP address has changed then that is something entirely different, you will have update your external dns records.MVP Exchange Server