There is a firewall with two NICs and the below rule to allow an
internal host to connect out to smtp servers on the internet. Some
hosts have a connection timeout on a connect from $INTERNAL_IP_OF_SMTP
yet connect from the firewall just fine.
iptables -t nat -A POSTROUTING -p tcp -o $NIC_EXTERNAL \
--dport 25 -s $INTERNAL_IP_OF_SMTP -j MASQUERADE
ex:
on firewall:
telnet csoc-mail-msfc.csoconline.com 25
above connects ok
on $INTERNAL_IP_OF_SMTP
telnet csoc-mail-msfc.csoconline.com 25
connection times out
