XFOR: Using Exchange As a Gateway Between UNIX and MS Mail (185153)


The information in this article applies to:

  • Microsoft Exchange Server 4.0
  • Microsoft Exchange Server 5.0
This article was previously published under Q185153
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

After an upgrade from Exchange Server version 4.0 to Exchange Server version 5.0, MS Mail users may be unable to reply to mail received by means of the Internet Mail Service. This can also occur in systems where custom recipients have been created in Exchange Server for users connected to Exchange by means of the Internet Mail Service. A good example is an internal mail system that uses the Internet Mail Service to connect to a UNIX based mail system.

CAUSE

To prevent spoofing (impersonating another person via Internet mail), Exchange Server version 5.0 does not automatically resolve the Reply To address to a friendly name. Therefore, when a user receives mail from the Internet Mail Service, the Reply To address is in SMTP format (user@company.com) instead of the display name associated with the SMTP address. When this mail is sent to the MS Mail user, the Reply To address remains in SMTP format. Without the Access component, this address can not be resolved by MS Mail, and a reply message will fail.

WORKAROUND

To resolve this problem, use one of the following workarounds:

Install the Access component that is supplied on the Exchange Server version 5.0 CD and has unlimited licenses on each MS Mail postoffice. Have them point to the shadow postoffice on the Exchange Server computer. This will allow MS Mail to correctly route the reply mail, but it will NOT show the friendly name in the Reply To field on the MS Mail client.

- or -

Modify the registry to enable Exchange Server to resolve Reply To addresses on messages received from the Internet Mail Service to Exchange Server friendly names. This option requires that Service Pack 1 be installed on the computer running Exchange Server version 5.0.

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. Click the Start button, and then click Run.
  2. In the Open box, type Regedt32.
  3. In the Windows Registry Editor, click HKEY_LOCAL_MACHINE on Local Machine on the Window menu.
  4. Double-click the System subfolder.
  5. Double-click the CurrentControlSet subfolder.
  6. Double-click the Services subfolder.
  7. Double-click the MSExchangeIMC subfolder.
  8. Double-click the Parameters subfolder.
  9. On the Edit menu, click Add Value and use the following value:

    Value Name: AddressRewrite
    Data Type: REG_DWORD
    Value: 1

  10. Locate the ResolveP2 value name; double-click it and change the value to 1. It should resemble the following:

    Value Name: ResolveP2
    Data Type: REG_DWORD
    Value: 1

When these parameters are set, Exchange Server remaps the Reply To address to the friendly name.
Modification Type:MinorLast Reviewed:4/21/2005
Keywords:kbprb KB185153
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