Question : Reverse DNS Question

Emails are failing to one of our customers. The returned email reflects the public ip, but not the host name (smith.com). I'm confident this is reverse dns issue. I need to contact my ISP, but I need some advice before doing so.

Our registed domain smith.hst.com is different from our mail domain which is smith.com.


Our ns1 record, "ns1.smithhst.com" is pointed to 65.175.184.129. This is only an example and not our actual company name or ip address. The referenced public ip is the outside interface of our fatpipe running SmartDNS, but is the ip that reflects in the mail headers on the failed email transmissions. Outgoing internet email goes across our internet T1 out to the internet. All incoming internet email, bound for smith.com, comes back, accross the internet to our corporate headquarters, across our frame connection to our local mail server located inside our network. That local mail server is on the smith.com domain. An example of our email address would be "[email protected]"

Would I setup reverse dns as follows:

129.184.175.65     IN        PTR   ns1.smithhst.com

I want to make sure that the mail  continues to be associated with the smith.com domain.
Currently the ISP is listed as the Primary DNS. At least that's what I noted a few minutes ago when I was doing an automated request for a Reverse DNS change. Perhaps I need to change the primary to our fatpipe. I may also need to create an MX record and point it back to the vestcom domain. I could create a seperate public IP just for the mail server and enter this on the fatipe.

Any suggestios?

Answer : Reverse DNS Question

>I want to make sure that the mail  continues to be associated with the smith.com domain.

What do you mean by that, exactly?

As long as you set your return address and Reply-To fields to be someone at smith.com, you won't have to worry about mail getting returned to some other domain (like hst.com), unless it is bouncing when you attempt the initial delivery (at which point it *should* bounce to hst.com, so that the delivery error can be corrected).

That being said, I don't think you need to worry about MX records - obviously one exists for smith.com and is pointing to the proper server, otherwise you wouldn't be getting a bounce (unless the MX is pointing to the *wrong* server, and then everyone at smith.com would be screaming about not being able to get their email, so that's obviously not the case).

You *do* need to get a PTR record added to the proper in-addr.arpa zone (184.175.65.in-addr.arpa domain , as PennGwyn points out) - if your ISP is handling your DNS, then I'd get them to add something like

129     IN     PTR     client1.smith.hst.com.

to their in-addr.arpa zonefile (it won't help to setup DNS locally, unless your ISP is willing to delegate authority for the proper in-addr.arpa zone, or subset thereof).

Also, I'd make sure that client1.smith.hst.com resolves to 65.175.184.129 - some mailservers check the PTR and A records to be sure that they match.

Cheers,
-Jon