Sending mail between 2 servers in DMZ via external IP
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 (mailserver.mydomain.com):
External IP: 220.127.116.11
Port forwarding set up for SMPT from 18.104.22.168 to 192.168.100.10 via either WAN or LAN
Other Server (listserv.mydomain.com):
If listserv tries to send an email to firstname.lastname@example.org then I can see that via DNS it is resolving to 22.214.171.124, 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 mailserver.mydomain.com then the second server will query DNS for a address resolution for mailserver.mydomain.com and in hosts it will find 192.168.100.10
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.
Thanks for your post - enabling NAT Reflection solved the problem!