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Q251124: XFOR: How to Configure Alias Table in Exchange Server

Article: Q251124
Product(s): Microsoft Exchange
Version(s): winnt:5.5
Operating System(s): 
Keyword(s): exc55
Last Modified: 21-FEB-2000

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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SUMMARY
=======

This article describes the difference in the way that Exchange Server and the
UNIX Sendmail program route Internet e-mail mail messages, and provides steps to
configure Exchange Server to use a connectivity structure that is similar to the
alias tables that are offered by the UNIX Sendmail program. The steps in this
article are not intended to replace common configuration concepts or guidelines,
but to provide a workaround that implements a connectivity structure that is
similar to alias tables.

MORE INFORMATION
================

In UNIX, the e-mail server program Sendmail can route incoming e-mail to various
Simple Mail Transfer Protocol (SMTP) hosts by looking up the recipient's e-mail
address and sending the e-mail message to the route that is defined in the alias
table by the system administrator. Alias tables can also change the intended
recipient's e-mail address before the e-mail message is relayed.

By default, the capability of Exchange Server to route e-mail messages by using
e-mail addresses is limited, because Exchange Server can only route incoming
e-mail by examining the recipient's domain name; it cannot route incoming e-mail
by examining the entire e-mail address. Unless all of the servers are deployed
in an Exchange Server-only topology with connectors, Exchange Server cannot
leverage the message transfer agent to route e-mail messages by e-mail address.

For example, if inbound e-mail messages are sent to someone1@microsoft.com and
someone2@microsoft.com and these recipients are homed on different servers that
have no knowledge of each other, the relaying Exchange Server computer that is
the entry point for microsoft.com cannot route the e-mail messages to the
appropriate mailbox servers. Instead, the relaying server routes the e-mail
messages to only one mailbox server, because Exchange Server has only domain
name-to-server mapping, and this example requires a route defined by user
name-to-server mapping, which is a feature of alias tables.

The following steps outline how to implement a connectivity structure that is
similar to alias tables. After you perform these steps, Exchange Server can
route e-mail by using the user name portion of e-mail addresses, and not just by
using the domain name portion. The following procedure assumes that Exchange
Server computers are the mailbox servers.

To configure an Exchange Server computer to route e-mail messages to mailbox
servers:

1. Create custom recipients (CRs) on the server that correspond to mailbox
  recipients on the mailbox servers. In the E-mail Addresses tab, make sure
  that each CR has the following properties:

   - An Internet-based address for directory lookup (for example,
     someone5@microsoft.com). Set this address as the reply address.

   - An internal routing address to use for mailbox server-to-routing server
     relaying (for example, someone5@expedia3.microsoft.com).

2. Click the General tab, and then modify the CRs domain-defined attribute (DDA)
  by clicking "E-mail address". For the DDA address, type an internal routing
  address to designate a mailbox server (for example,
  someone5@expedia3.microsoft.com). After you perform these steps, Exchange
  Server changes the recipient's e-mail address to this newly defined DDA
  address before it sends a message, as the UNIX Sendmail program does.

3. Click the Connections tab in the Internet Mail Service, and then click E-mail
  Domains. Add each internal routing subdomain (for example,
  expedia3.microsoft.com) along with the IP address or the fully qualified
  domain name of the corresponding mailbox server.

4. Click the Routing tab of the Internet Mail Service, and then click to select
  the "Reroute Incoming SMTP mail" check box. To prevent unauthorized relaying,
  specify only the mailbox servers by clicking Routing Restrictions.

To configure each mailbox server to accept e-mail messages that are addressed to
its internally routed recipients:

1. Ensure that each mailbox recipient has at least the two following addresses:

   - A reply address of the primary domain name (for example,
     someonex@microsoft.com).

   - A secondary proxy address that corresponds to the internal routing entry
     (for example, someonex@expedia.microsoft.com).

2. Click the Connections tab of the Internet Mail Service, click "Forward all
  messages to the host", and then designate the routing Exchange Server
  computer.

If you want to use third-party messaging products instead of Exchange Server
computers as the mailbox servers, make sure that the third-party messaging
products are configured to send e-mail messages back to the routing Exchange
Server computer, and to send outbound e-mail with a reply address that uses the
original domain name (for example, someonex@microsoft.com). Make sure that you
enable the RerouteViaStore registry on the routing Exchange Server computer, in
case UNIX servers or POP clients cannot change the reply address and need to
relay messages back to the routing Exchange Server computer for e-mail message
delivery to the Internet. For additional information, click the article number
below to view the article in the Microsoft Knowledge Base:

  Q238471 XIMS: How to Force SMTP Messages Through the Information Store

Additionally, you can use any domain name for internal routing, instead of the
subdomain approach outlined in this procedure.

Any changes to the configuration of the Internet Mail Service require that you
stop and restart the service.

Additional query words: "alias table" IMS

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Keywords          : exc55 
Component         : IMS
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbhowto

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