One hostname per RDNS entry? 1

[monsterjta]

Currently, I host email for multiple domains...all going to one Exchange Server. I have one public IP routing to my Exchange, with all domains using that IP. So, my RDNS has only one hostname bound to it.

Can I have my ISP bind more than one hostname per RDNS entry? Or, do I need to route a different public IP for each domain being hosted to my Exchange server to accomodate for "true" RDNS records? It works fine as is, but it might be nice for a reverse lookup to reflect each domain with their actual domain name...

Thank for your feedback!

 

[nsantin]

Not sure about the RDNS record, however you might want to setup a SPF record for the domains that don't match the mail server name. This will prevent mail from getting tagged as spam

 

[ShackDaddy]

Monster, you're kind of approaching the situation backwards... Typically admins in your situation don't create an A record for a mail server in each domain and then point their MX record at that A record. Usually you create each domain, and then point the MX record at a single common name that won't necessarily be in the domain that the mail is to go to. That way all you need is a single RDNS record. Because in fact, you can only have one.

So if I manage mail for 'luckylaw.com' and 'pinktop.com' and 'gourmetclod.com' and all have mail going to the same server, I would pick one of the domains and create an A record that resolves the external server IP.

server 66.55.44.33 luckylaw.com

Then on each domain, I would create MX records:

MX for luckylaw.com = server.luckylaw.com
MX for pinktop.com = server.luckylaw.com
MX for gourmetclod.com = server.luckylaw.com

Then have the ISP create an RDNS record that maps 'server.luckylaw.com' to the right IP.

If you don't want someone digging in the DNS on the outside to see that two particular domains are affiliated, you could create an A record on some other domain like a management domain 'monsterconsulting.com' that points to the external IP of the mail server and then point all those other domain's MX records at that name. Then looking at the message header for mail from 'pinktop.com' wouldn't show that they were really "in bed" with 'luckylaw.com'.

Does that make sense? That's really the right way to do this, and the way things are built out there. There's a satisfaction in having each domain have its MX record point at an A record in its own zone, but it's not realistic when hosting multiple domains on a single mail server.

ShackDaddy

 

[monsterjta]

I understand what you're saying. However, I do not have direct access to our hosted customers' DNS registrar and all of this was setup prior to coming on-board this this company. I would love to have all our client transfer their registrar to ours, so that I can control these things more easily. Half the time, when I ask a customer to change a record, it takes days (sometimes weeks) because they don't have access to their own registrar for crying out loud

We already have our RDNS record in place for all customers as you desribed above. I was just hoping that we could "make it there own" by giving them there own RDNS entry. But, it's all irrelevant to the base functionality.

You did give me the answer by stating "Because in fact, you can only have one", so I will award you for the input.

Thanks!