Network issue

Hi
I am new to Linux networking. I have configured one linux machine as a proxy (squid) and 3 other linux machines use this proxy to connect to the internet. The problem is that I am not able to configure any mail client on the 3 machines. When I try to configure KDE or any other mail client o access a pop3 account (say yahoo), it gives an error message 'host not found'. Also I am not able to ping to any external IP from these 3 machines. Any idea how to solve this ?
Thanx
Biju Nair

The proxy you have set up (squid) is only an HTTP proxy, it has nothing to do with the rest of the protocols, so DNS requests, SMTP and POP messages, ping packets and so on have nowhere to go.
You probably have only a single IP address for your "proxy" machine. If so you need to make it a gateway as well as a HTTP proxy, so it can translate your local IP addresses on your network to the real IP address of your internet connection.
Setting up such an address-translating gateway may either be simple or complicated, and it largely depends what software you already have installed and configured on the proxy box.
Many people, myself included, prefer to install one of the specialist distributions (e-smith, smoothwall etc.) on such a box, as it does it all for you. What have you got installed already? and do you need that box to do anyting else other than act as a gateway, proxy and mail router?

Hi Frank,
Thanx for the reply.
I am running RedHat 7.1 on that machine. And except for squid, there are no other software installed ( specific to networking) on that machine. I plan to use it as proxy, gateway and an IMAP (which I have not installed and configured yet) mail server.
Thanx
Biju Nair