XFOR: Attachment Extensions Handled Differently in Exchange 5.5

With Exchange 5.0 and 4.0, the attachment file names received and sent through the Internet Mail Service (Internet Mail Connector in 4.0) may be altered. For more information regarding this behavior, consult the following Microsoft Knowledge Base article: With Exchange 5.5, the attachment file names received and sent through the Internet Mail Service are preserved.

This change was made in an effort to better preserve message fidelity (the ability to reconstitute a message exactly as it was received for later resubmission), and due to customer demand.

The Exchange Server versions 4.0 and 5.0 behavior can be restored by implementing a registry value change as documented below.

Exchange 5.5 offers a mechanism for restoring the Exchange Server 4.0 and 5.0 behavior with respect to file name extensions. It is recommended that customers not enable this feature, because it has the effect of preventing some document handlers from working properly. It is also possible that this mechanism will be unavailable in future versions of Exchange.

Consider, for example, the vCard Internet standard. The vCard standard calls for a <FILE>.VCF file to be sent as a text/plain attachment. In Exchange 4.0 and 5.0, the attachment is renamed to <FILE>.TXT, and a user double-clicking on the attachment invokes the document handler for .txt files, instead of the vCard document handler associated with .vcf files.

If you still want to enable this mechanism, here are the instructions for adding the required registry value:

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

1. Run Registry Editor (Regedt32.exe).
2. Go to the following key in the registry:
   

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS
      \ParametersSystem\InternetContent
   						

   
   NOTE: The above registry key is one path; it has been wrapped for readability.
3. On the Edit menu, click Add Value and use the following entry:
   

         Value Name: RemapExtension
         Data Type:  REG_DWORD
         Value:      1

4. Exit the Registry Editor and restart the information store service for the change to take effect.

Setting the RemapExtension to 1 causes the information store to restore the Exchange 4.0/5.0 behavior as described in 147299  (http://support.microsoft.com/kb/147299/EN-US/ ) . To restore Exchange 5.5 behavior, either delete the registry value or set it to a value of 0 and restart the information store.