Topic Last Modified: 2008-03-11

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether the SMTP proxy address for Exchange ActiveSync® has been overridden:


If the Exchange Server Analyzer finds the SMTPProxy registry entry present and configured, a non-default configuration message is displayed.

SMTP addresses are used to identify the path of a mailbox in Exchange Server, and they must be unique. Each address has a left-hand side (LHS) portion and a right-hand side (RHS) portion that are separated by an @ symbol. For example, the format for an SMTP address is as follows: = left-hand-side@right-hand-side (or LHS@RHS)

Exchange ActiveSync uses a WebDAV request to access the mailbox information from the Exchange server. Exchange ActiveSync selects an associated RHS value, with the LHS@RHS representing an SMTP proxy address, to use in the WebDAV request. In environments that have a default RHS address that is different from a user's primary SMTP address, the SMTPProxy registry value provides a configuration opportunity to allow Exchange ActiveSync to use an alternate SMTP proxy address.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To view or modify the SMTPProxy registry value

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to:


  3. Examine, and if desired, change the SMTPProxy value.

  4. If a change is made, close the registry editor, and then restart the Exchange Server computer for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information about Exchange ActiveSync, see "Exchange Server 2003 ActiveSync Architecture" (

For more information about mobile access and Exchange Server 2003, see "Mobile Messaging with Exchange ActiveSync" (