Hi all,

Here is my set up.

Below is part of my iptables

mail ip =

#PAT for OWA, smtp and pop from public IP to exchange behind the firewall
$IPT -t nat -A PREROUTING -p tcp -i $INET_IFACE -d $public_IP --dport 25 -j DNAT --to
$IPT -t nat -A PREROUTING -p tcp -i $INET_IFACE -d $public_IP --dport 110 -j DNAT --to
$IPT -t nat -A PREROUTING -p tcp -i $INET_IFACE -d $public_IP --dport 443 -j DNAT --to

#NAT internal LAN for internet access

Here is my situation in details:

1) I can receive mail from public without any problem
2) From LAN I can send mail to punlic domain without any problem.

Here is problem:
1)From internet I can logon to OWA and sending mail ok
2)I can use outlook to connect to exchange by pop3 and receive messege Ok but when I send mail to user in the same domain or public domain from here I get this error messege

"Reportde error (0x800CCC78 ) : 'Unable to send the message. Please verify the e-mail address in your account properties. The server responded: 454 5.7.7 Client does not have permission to submit mail to this server.'

and a RDN in the inbox is
The following recipient(s) could not be reached:

'user@address..' on 11/08/2006 7:36 PM
550 5.7.1 Unable to relay for user@address...


I am pretty sure it is the Linux box problem as it was working fine before.

Thanks heaps.