Sending mail between 2 servers in DMZ via external IP

  • Hi Everyone,

    I have two servers in my DMZ.  One is an email server, the is a list server which is trying to send emails to (amongst other places) the email server in the DMZ.

    What I have got in effect is:

    Mail Server (
    External IP:
    Port forwarding set up for SMPT from to via either WAN or LAN

    Other Server (

    If listserv tries to send an email to then I can see that via DNS it is resolving to, but then times out when it tries to send the email.

    I'm guessing that I might need another rule to get the SMTP traffic from DMZ back to DMZ again?

    Could someone give me some suggestions?


  • On the second server you can simply add a line in your hosts file saying that the server one is at "that" ip address … Then the second server will query your DNS for MX records you'll get then the second server will query DNS for a address resolution for and in hosts it will find

    You could also try enable NAT Reflection or in fact Disable the option saying "Disable NAT Reflection" in the System -> Advanced configuration page. This will allow internal network to access local services using external ip address for all your port forwarded services.

  • Hi MageMinds,

    Thanks for your post - enabling NAT Reflection solved the problem!