Can the Exchange ISP domain name and local domain name be the same?

Domain Controller
Global Catalog Server
Microsoft Exchange 2003
I’m looking for some assistance with designing an Exchange Server 2003 structure to replace Lotus Notes. My company has two locations, a head office and a factory. They’re 140 km apart. There are 35 users at the head office and 150 users at the factory. We have a RF-Lease Line 128 Kbps connectivity. The Internet connectivity is ADSL 256 Kbps at the head office and 128 Kbps at the factory. I want to put one domain controller (DC) and Exchange server at the head office and one DC and Exchange server at the factory in the same domain. Both servers will act as Global Catalog servers and will fall in the same Exchange Server organization. At both sites, fetching email from Internet Service Provider (ISP) mailboxes will be done by Linux Fetchmail using their own Internet connections. In order to route external email using a smarthost (the ISP's own SMTP) at both sites, outgoing email must go through their Internet connection and internal email must go through the lease line connection. What will happen if the ISP domain name ( is the same as the local domain name ( Should the local domain name be different from the ISP domain name?

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The MX record should be pointing to your own Mail server. If you create a new MX record pointing to an external IP I fear that it will mess up your internal email as well. Just a thought but ain’t sure and perhaps you can have a try. If it works then great otherwise just take it off again and things should be back to normal (make sure DNS has been replicated)

Another way to resolve this is to create a POP3 account in Outlook and use that account ONLY to send email to this particular company. Make sure you enter your SMTP server name (the one given to you by ISP) and NOT your mail server name in SMTP Server. Also need to open Port25 on the fireware (router) to allow email being sent from clients.

However I do not favour this solution. I’d rather rename my domain name.

Depending on how you have DNS setup, you can have SPLIT DNS such that there is an internal MX record pointing to an internal host/IP. The external MX record can point to a public IP for a firewalled internal host.

After further reading…. the only role DNS plays in this situation is routing the outbound SMTP traffic. Inbound sounds like a pull event. For outbound SMTP relay, you should be okay with the same internal and external domain names as long as the host part of the name is unique to each side of the network edge. For example, the ISP’s SMTP relay may be called and the internal hosts would have names like and There should be no fear of DNS name collisions if you set things up along these lines.

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  • Dwiebesick
    One of the better articles on this subject is from Thomas W Shinder, I have used his instructions on several customer installs. Check it out and see if this is what you are looking to do. dmw
    2,235 pointsBadges:
  • Jaideep Khanduja
    I don’t think it will have any effect as besides a common domain name all other entities will differ, so it will not effect your communications.
    19,810 pointsBadges:

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