XADM: How to Set Up Centralized SMTP Domain Sharing in Exchange 2000 Server for Independent Organizations

In an enterprise, there may be several distinct Exchange organizations and other e-mail systems that share their Simple Mail Transfer Protocol (SMTP) domain. This article describes how to centralize incoming and outgoing e-mail in such an enterprise. To centralize e-mail, you use an Exchange organization as a mail hub. To do this, you set up mail-enabled Microsoft Windows 2000 contacts with the primary SMTP-address for the shared SMTP domain, different SMTP target addresses, and selective SMTP connectors for routing.

If you have multiple e-mail organizations that share a common domain, you may want a centralized mail hub for inbound and outbound SMTP traffic.

You may want all e-mail to leave the enterprise with a consistent mail address of @organization.org. You may want all incoming e-mail for the SMTP address @organization.org to be centrally queued and correctly routed to the appropriate e-mail organization. For example, imagine the following situation:
Enterprise Organization

• E-mail hub Exchange 2000 Organization A with main SMTP address @organization.org.
• Exchange 5.5 Organization B with main SMTP address @organization.org.
• Acquired Exchange 5.5 Organization C with main SMTP address @acquired.org.
• UNI- based e-mail Organization D with main SMTP address @organization.org.

To set up the Organization A as a SMTP mail hub for the whole enterprise and a consistent mail addressing with @organization.org, follow these steps:

1. Create the following SMTP addresses:
   1. @subb.organization.org for mail recipients in Organization B.
   2. @subc.organization.org for mail recipients in Organization C.
   3. @subd.organization.org for mail recipients in Organization D.
2. Set up a Recipient Policy in Organization A with an address space of @organization.org. Make sure that the This Exchange Organization is responsible for all mail delivery to this address check box is selected.
3. For each mail recipient that is in the enterprise but outside organization A, set up a Windows 2000 contact with:
   • The primary SMTP address of user@organization.org.
   • A target address of user@subx.organization.org.
     
     NOTE: You can set up a target address of the Windows 2000 contact, different from the primary SMTP address of the contact in Active Directory Users and Computers only with Exchange Server 2000 Service Pack 2. For more information:
     309212� XADM: Cannot Set Secondary Address as Primary on a Contact
     For Exchange Server 2000 pre-SP2, you can change the target address of the contact through ADSIEdit or LDP tools from the Windows 2000 Support Tools on the Windows 2000 Server CD.
4. For every subx.organization.org, set up an SMTP connector with the address space of subx.organization.org. Set the routing appropriately, either to a smart host for these subdomains in these other mail organizations, or through an internal DNS solution.
5. Set up appropriate SMTP connectors with all SMTP address spaces that are accepted for your enterprise (for example, the address space @aquired.org for mail organization C). Set the routing appropriately either to a smart host for these subdomains in these other mail organizations or through an internal DNS solution.
6. To centralize outbound SMTP traffic through Exchange 2000 Organization A, you must set up the appropriate mail connectivity from Organizations B through D to Organization A. Because the main SMTP-address of the Windows 2000 contacts is @organization.org, recipients in the Organizations B through D appear outbound with this SMTP address.

For additional information about setting up mail-enabled Windows 2000 contacts, click the following article number to view the article in the Microsoft Knowledge Base:

For additional information about adding secondary SMTP-Proxy addresses in bulk for Exchange 5.5 organizations, click the following article number to view the article in the Microsoft Knowledge Base: