Hi there;

I had a couple questions which are probably pretty basic for most of you here.

What should the PTR record point to?

Let's say I have 3 IPs
192.168.1.1
192.168.1.2
192.168.1.3

I also have a main domain, two nameservers, and other domains hosted on the same box.

ns1.domain.com -> 192.168.1.1
ns2.domain.com -> 192.168.1.2
all domains -> 192.168.3

What do I want the PTR to be?

Am I looking to have the PTR resolve to the domain name of the nameservers, or the mail servers?

And let's say that I have multiple domains, each running their own mailserver. If they share an IP they obviously can't have their own rDNS. Will this cause a problem?

I apologise if this got confusing.

Thanks,

Cam

Here's a post that covers a lot of rDNS info, it should help you out.

http://forums.devshed.com/showpost.php?p=649015&postcount=3

I sympathize with your confusion, since rDNS is very non-intuitive. Here is rDNS for dummies from someone who has gone through it:

First, identify what IP address your mail server actually sends from. In my case, it was the lowest of the range of IPs assigned to the machine by my web host, and it was not something I could configure. My mail server actually receives messages on several IP addresses, but always sends out on one.

Second, figure out what domain your mail server uses to identify itself. In my case, this was a single configurable value -- something I input. Of course, the server is handling mail for several domains, but it always identifies itself in message headers as one in particular (which usually does not match the domain of the from address in the message, but that doesn't seem to matter).

Now -- ask your host to create a PTR for the IP address your mail server uses to send, and the domain listed in the PTR record should be the domain your mail server uses to identify itself. Then, when a receiving mail server reverses the IP address used to connect (which is not something you could fake), it finds out that your mail server is telling the truth about who it is.

This setup seems to cause happiness downstream.

you can have only one PTR per IP, so just set it to your server hostname to work properly for mailservers that doesn't accept email from non-PTR IPs

You should use the following PTR records:

1.1.168.192.in-addr.arpa -> ns1.domain.com
2.1.168.192.in-addr.arpa -> ns2.domain.com
3.1.168.192.in-addr.arpa -> some A record that points to 192.168.1.3