Ask the Expert

Separating domains while keeping existing Exchange Server email IDs

We have the following setup:

Location 1

  • Forest Root
  • Domain Name:
  • DC:
  • ADC: (having Exchange 2000)

    Location 2

  • Domain Name:
  • DC:
  • ADC: srv2. (having Exchange 2000)

    Internet email ID across both domains:

    We want to migrate to Windows 2003 and Exchange 2003 on new hardware. At the present time, we are in the planning stage, which will be followed by testing in a lab environment. We would like to know how to proceed for the following queries:

    1. We want to separate the two (Windows) domains -- i.e., we do not want a single forest (so that there is no dependency between the two). We can change the email IDs to "" and "" But for some users (in both locations), we also need the "" address. How do we accomplish this?
    2. We want to separate the two (Windows) domains (as above), but we want to keep the same email IDs ("").
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    To answer your first question, if you maintain a single forest, with two domains -- this is a non-issue. You simply have the proper proxy addressing on the objects, and native mail flow will work as designed.

    As for your second query, two separate domains can share in the corporate name space. Just configure the Recipient Update Service and SMTP gateway to accept mail. Also, make sure your MX record is pointing to the appropriate SMTP gateway.

    Do you have comments on this Ask the Expert Q&A? Let us know.

    Related information from

  • Expert Advice: Joining an existing AD forest vs. creating a new one
  • Tip: Pros and cons of multiple Exchange Server organizations
  • Learning Guide: Exchange Server migration
  • 15 tips in 15 minutes: Managing recipients and distribution lists
  • Reference Center: Exchange Server and Active Directory resources
  • This was first published in July 2006

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