How to configure DNS to send mails to a partner's domain that is the same that our local domain

I'm working in a company that some time ago had to be divided in 2. So, now we have Company-1 and Company-2 and both are completely independent. Recently the other company choose a public domain name that is exactly the same that our Active Directory domain name and now when we send mails to them, it stucks in queue with a "Cannot connect to remote host" message.

How can I solve this?

Thanks in advance
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Remove the active directory domain name from the Exchange Recipient policies. Make sure you have your internet domain name listed in the recipient polices.
Possible Workaround: Open the Exchange recipient policies in the system manager, double click on the policy concerning the domain name of the client  and uncheck the option "This Exchange Organization is responsible for all mail delivery to this address."

The first suggestion is nicer/better if you ask me.
Nuno MartinsCommented:
That situation is very unlucky :)

Ok, what I recommend you to do is to rename your local domain name from AD.
We could resolve the e-mail situation by creating a smtp connector or maybe using the solution refered above but other problems could come from that kind of situation &. This why Microsoft recommends never to use public domains on your active directory .

To rename your AD here are some articles that explain how to do it:
Windows Server 2003 Active Directory Domain Rename Tools
How Domain Rename Works

If you don´t want to do that kind of operation and you prefer to stay as you are (Not Recommended in my opinion)
Try creating a SMTP connector for the domain and specify manually the ip of theirs e-mail server
oswaldofarithAuthor Commented:
I'm not using Exchange and I don't want to rename the AD domain, so, it is possible to make a workaround using DNS only?
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You had the name first, make them change it!
Do not rename your domain for this !
What e-mail server are you using ? Check the dns settings for the mail server, it should lookup the MX record for the domain.  Usually there is not an MX record in the AD dns. The solution should be searched in the mail server / dns setup you're using. Having the same AD domain name shouldn't be a problem if you configure your mail sever correctly.

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oswaldofarithAuthor Commented:
I'm using Kerio Mailserver for Windows Server 2003.

I get the point, so I will search in Kerio documentation.
Look at the optios for setting to use a smarthost for mail delivery, if possible for certain domains.
Nuno MartinsCommented:
Has you probably know that kind of settings that oswaldofarith is using on the internal domain, can bring him a lot of problems. What is happening is just one example. So recommending some one not to permanently resolve the issue, i don´t think is a good idea.
But the Admin of the system as the last word on the subject.

To resolve the issue without having to rename using kerio mailserver check this link:

There you can see where you can create an SMTP/relay:
Relaying is configured under Configuration->SMTP Server

oswaldofarithAuthor Commented:
What I had to do to solve this problem was to create a new domain without users, with the name of the other company (the same that I using in AD) and in the Forwarding option, mark "If recipient was not found in this domain, forward the message to another host" with the IP of the partners mailserver. Thanks to buddhole and the other guys for your help.
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