I am fooling around with iptables to mold a linux box into a gateway for my network.
I used the following basic commands

modprobe iptable_nat
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forward

this seems to be working perfectly fine except that when I try to attache
a file to an email I am sending from hotmail it takes a lot of time and the
process fails with the following response

Cannot find server or DNS Error
Internet Explorer
I tried the same process using the IPs assigned to me by my ISP
and all seems to be working fine until I try to do it from behind the

Can you guys help me analyse the issue?

Thank you.