XADM: MIME Type Extension Mapping Not Used for Attachments w/out Extensions from Internet

With Exchange Server versions 4.0, 5.0, and 5.0 Service Pack 1 (SP1), the attachment file names received and sent through the Internet Mail Connector in 4.0 and the Internet Mail Service in 5.0 may be altered. For more information regarding this behavior, consult the following Microsoft Knowledge Base article: With Exchange Server versions 5.0 SP2 and 5.5, the attachment file names received and sent through the Internet Mail Service are preserved, unless the "RemapExtension" registry value is set to 0x1 as specified in the following Microsoft Knowledge Base article: There is currently no configuration for Microsoft Exchange 5.0 SP2 and 5.5 that will preserve file name extensions for attachments with extensions, but use MIME Type mapping for attachments without extensions.

The RemapExtension registry value (as mentioned in 182083  (http://support.microsoft.com/kb/182083/EN-US/ ) ) forces a MIME Content-Type extension remapping for all inbound attachments.

To resolve this problem, obtain the latest service pack for Exchange Server version 5.5. For more information, please see the following article in the Microsoft Knowledge Base:

Exchange Server 5.0 SP2

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0 SP2.

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next service pack that contains this fix. Contact Microsoft Technical Support for more information.

This fix has been posted to the following Internet location:


Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.5. This problem was first corrected in Exchange Server 5.5 Service Pack 2.

A new value has been defined for RemapExtension (0x2). After applying the fix mentioned above, a new registry value must be set as described below.

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:      2

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

Setting the RemapExtension to 2 causes the information store to remap the extensions based on MIME Content-Type for attachments that do not have an extension already.

Setting the RemapExtension to 1 causes the information store to restore the Exchange 4.0 or 5.0 behavior as described in 147299  (http://support.microsoft.com/kb/147299/EN-US/ ) .

To restore Exchange 5.5 behavior default behavior, either delete the registry value or set it to a value of 0 and restart the information store.

Here are the combinations:

RemapExtension REG_DWORD 0x0 (or missing)
(Default Exchange 5.0SP2 and 5.5 behavior; don't remap anything regardless of extension)

RemapExtension REG_DWORD 0x1
(Old Exchange 4.0, 5.0, and 5.0 SP1 behavior, documented in 147299  (http://support.microsoft.com/kb/147299/EN-US/ ) ; remap everything based MIME type)

RemapExtension REG_DWORD 0x2
(New behavior; remaps only those attachments with no extension.)