Can't check external mail through my server

[brasi]

I Have a server with Fedora Core 4, squid proxy, iptables, dovecot (was pop3), sendmail, openwebmail, etc.

On my LAN all works great... but can't check external servers for mail.

On a client (windows) i do a ping to the server and i get response with good conection...
100% packets ok.

but if i do a telnet to the same external server.... my server respond the query.... not the server what i'm try to get data...

telnet mail.external.net 110
-> +OK Dovecot Ready....

i'm missing something in the iptables??
i do a echo 1>/proc/sys/net/ipv4/ip_forward

there is a special chain to add to iptables to forward the trafic fomr port 25 and 110 if the address don't match my server?

Thanks in advance!!

[yourname3232]

Is your server behond a router? If so then you would have to forward ports to your linux box. If you don't then requests form the outside world will be dropped.

[brasi]

My server linux have 2 ethernet cards.... the request from outside can be served like webserver, sendmail, etc... (have static ip)

but if i am a client of my server (LAN)... i can't check another mail, only my internal mail with the outlook...

(client) <----> (serverinternal) <-----> (another server)
packed to another..------>>|

if i configure a second acount on the outlook (an external one).. only ,my sendmail respond... cant reach the external mail server...

like i wrote before...
telnet server.external.net 110
> internat.server.net ok... (responding and not the external one.)

ping to the external server is ok. 100% packed ok

how can i forward that packed if both servers use ports 25 and 110? my server (internal) and another external server (any server...)???