Hello,
Thanks for all previous help.

Now I am able to telnet both port 25 and 110
from gateway machine to client machine and
from client machine to gateway machine.

Both system are On Mandrake 10.1 off.

Gateway machine :
eth0 is WAN witn static IP connected to 512Kbps DSL
eth1 is LAN.

Client system :
eth0 is LAN.

There is no firewall or router installed on any system.

My ISP is not blocking .

Still I am not able to send or recieve mails through
the gateway machine.

Why ?

Now where is the problem ?

How can troubleshoot ?

Thanks again

Varun

Ok but you still haven't tested going from the CLIENT directly to the server beyond the gateway machine.

E.G. if your ISP's mail server is called

mail.myisp.com

Then try

telnet mail.myisp.com 25

And see if you get a response.

Remember that if your Linux box is acting as a gateway, you'll need to set up some sort of NAT firewalling for the clients to get Internet access.

It doesn't sound like you've done this.

Telneting ISP's mail server yields :

[varun@saamail varun]$ telnet mail.vsnl.net 25
Trying 203.200.235.182...
telnet: connect to address 203.200.235.182: Connection timed out
telnet: Unable to connect to remote host: Connection timed out
[varun@saamail varun]$

same for port 110.

Basically clients are able to surf the net using squid proxy.

Is it necessary to do NAT / firewalling on gateway machine now ?

I was going to do that later.
First I wanted to get the mails thru.

Thanks

Varun

Most web browsers can utilize a proxy connection, but e-mailers (usually) cannot.

YES you need to set up NAT and put your client(s) behind your NAT firewall.

Your client cannot get out because it is effectively using a bogus IP which your ISP (and Linux box) cannot route.

NAT effectively gets the client to utilize the (working) Linux box's eth0 connection to the Internet.

(Read up a bit on NAT to get a better explanation...).

At the same time the NAT client is protected from the internet.