I am trying to find out if i need and how to set up PTR in the mycompany.com zone for my mail server and I refer to this qoute from http://forums.serverbeach.com/showthread.php?5469-Setting-up-PTR-s-(aka-Reverse-DNS)
Now, let's look at what happens when a mail server receives mail. A mail server receives mail from an IP address. The mail server then does a PTR look up on that IP address and retrieves a domain name. It then does a DNS lookup on that domain name and retrieves another IP address. If that IP address that it retrieves matches the IP address that the mail originated from, the mail passes the Reverse DNS check, and the mail is delivered. If the IP's do not match, or a PTR is not set up, or the domain does not resolve, then the mail is not delivered.
If my mail server is behind a firewall, would my IP still appear to the receiving server as the IP for mail.mycompany.com? Wouldn't it appear as the IP of the firewall?
EDIT: Sorry for the bad question, the truth is i am suddenly quite confused.
According to my understanding there are 2 ways to reach my (mail) server behind a firewall.
- I have 1 WAN IP (static or dynamic) assigned by ISP. External servers connect to me at that IP and firewall port forward to the mail server at LAN IP.
- I have a range of WAN IP (static) assigned by ISP. ISP forwards all the IP to my firewall. My firewall checks the IP and forward/switch to my mail server which we internally assign it the IP.
What will the IP appear to other servers if instead my mail server connects to them in each case?
EDIT 2: OK everyone, thanks for the responses, but really, my question is not "How to set up PTR for mail server"; it is "What is the IP of mail server behind firewall" in the above 2 cases stated. I think I wasn't clear enough, sorry about that.