XCON: Message Transfer Agent Can Now Set Reply To Address Based on the X.400 Connector Used

A new feature exists in the Microsoft Exchange Server Message Transfer Agent (MTA) that allows the MTA to select the reply address. The MTA can select the appropriate X.400 Reply To address for messages that are sent through a particular X.400 Connector by originators who have multiple X.400 proxy addresses. This capability is now available in versions of Microsoft Exchange Server version 5.5 later than Service Pack 3.

This feature requires that you create a registry key for each X.400 Connector. You must create this registry key with the name of the X.400 Connector. In addition, you must create a new string value named Site Proxy Override under the registry key for each of the X.400 Connectors. The Site Proxy Override registry value must contain the X.400 proxy address format that you want to use to set the reply address for all of the messages that are sent through the connector. The Site Proxy Override value must consist of a string in the following format: For additional information about the latest service pack for Exchange Server 5.5, click the article number below to view the article in the Microsoft Knowledge Base:

To enable this feature in a multi-X.400 proxy site, implement registry keys and values on the bridgehead server by using the steps outlined in the following example. In this example, the following conditions exist:

• All of the users in a site have two X.400 proxy addresses that have differing administrative management domains (ADMDs):
  c=US;a=xx;p=ExchangeOrg
  c=US;a=yy;p=ExchangeOrg
• There are two X.400 Connectors configured on the bridgehead server for this site. Each X.400 Connector is configured to connect to a different X.400 service provider. One connector is configured to connect to ADMD xx and the other connector is configured to connect to ADMD yy. The two X.400 Connectors are named the following on the bridgehead server:
  X.400 Connector to xx
  X.400 Connector to yy
• You want the MTA to select the reply to proxy address so that all of the messages that go through the X.400 Connector to xx have a reply address in the following form:
  c=US;a=xx;p=ExchangeOrg
  Likewise, you want the reply address for the originator of messages that pass through the X.400 Connector to yy to use the following proxy form:
  c=US;a=yy;p=ExchangeOrg.

You need to create two different registry keys on this bridgehead server:

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

1. Start Registry Editor (Regedt32.exe) on the bridgehead server.
2. Locate the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeMTA\Parameters
3. On the Edit menu, click Add Key.
4. In the first Key Name box, type the name of one of the X.400 connectors. For this example, type X.400 Connector to xx. Click OK.
5. In the left pane, click the new registry key so that it is selected.
6. On the Edit menu, click Add Value.
7. Type the X.400 proxy format that you want to use for this X.400 Connector. For this example, type c=US;a=xx;p=ExchangeOrg. Click OK, and then click OK again.
8. Repeat steps 2 through 7 to configure the settings for the other X.400 Connectors on the bridgehead server.
9. Quit Registry Editor.