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Multiple Domains and Reverse DNS with Exchange 2010

Posted on 2010-08-17
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Last Modified: 2012-05-10
I host multiple domains and some customers are not able to use Craigs List because they are matching the senders from address to the reverse DNS response of the sending mail server.  Since they don't match, mail is being rejected.  Is there any way around this?

This has been discussed before, but I didn't see a solution:

http://www.experts-exchange.com/Networking/Protocols/DNS/Q_23141108.html

I don't think that this solution answers the real problem here at all.   We have this problem too and we have our SMTP server in Exchange configured properly.   The problem is that when you have two domains "abc.com" and "2abc.com" and let's say "abc.com" is the main domian, and the DNS entry for the box matches "mail.abc.com" and the reverse IP lookup also matches that "mail.abc.com" then you decide to send a message out as "2abc.com", the domain that it is being sent from doesn't match the domain that you say you are "from" in your reply to etc.    Some SPAM filters will see that this is a relay and will automatically block you from doing that.   I don't think you can have 2 domains on a reverse IP lookup and/or perhaps that won't work properly all of the time.

The bottom line is for us we have 2 domains, one is our main company, and the 2nd is for our product.  We send email for our product from our data center which is not in our company, and then we also do tech support, but have a help desk in our offices, so we also send out email for "2abc.com" on our exchange server, and sometimes we are being blocked because the reverse IP for that machine points to "abc.com" not "2abc.com"
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Question by:exlinechris
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by:Alan Hardisty
ID: 33459809
Technically speaking - as long as the sending IP, Reverse DNS and FQDN of the sending server resolve to each other then there should not be a problem.
Would you like to disclose the domain names you are having problems with (which I will obscure immediately) and then I can run some checks and report anything incorrect about your setup?
Alan
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Alan Hardisty earned 2000 total points
ID: 33460102
Okay - it seems you have 2 MX records mx1 and mx2.yourdomain.com.  Both IP's have Reverse DNS setup properly and point to separate IP Addresses.
When connecting to both IP's on port 25, they both respond as mx2.yourdomain.com, so if you are sending via mx1 IP, that is where your problem could be because the server is saying I am MX2 but the IP resolves as MX1.
If you send via MX2 IP, then there shouldn't be a problem.
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