XFOR: IMS Failing to Decode Uuencoded Attachments

UUEncoded body parts within a message received via the Microsoft Exchange Server Internet Mail Service (IMS) are not decoded into an attachment. Instead, they are left as UUEncoded text within the message.

If a message includes a valid MIME header stating that the contents should be text, then the above behavior is by design. However some messages will contain partial MIME headers with UUEncoded bodyparts. In the case of a CONTENT-TYPE header being present (without a full MIME version header), the Microsoft Exchange Server will assume the message to be MIME and will not decode the UUEncoded body parts. The information in the rest of this article describes how this behavior can be modified so only valid MIME messages are treated this way.

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

A new registry key value has been created for the Information Store to control this behavior.

1.	Start Windows NT Registry Editor. Use Regedt32.exe if you are running Windows NT 3.51 and either Regedit.exe or Regedt32.exe for Windows NT 4.0.
2.	Create the following registry value: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ ParametersSystem\InternetContent Value Name: ContentTypeEQMimeVer Data Type: REG_DWORD Value: 0 or 1 (default is 1)
3.	Exit Registry Editor. Stop and restart the Microsoft Exchange Information Store for the change to take effect.

Setting this value to "1" means that if a top-level "Content-Type" header is found in an inbound Internet Message, the message is treated as a MIME message even if a "MIME Version" header is missing. Setting this value to "0" means that an Internet message is treated as a MIME message ONLY if a "MIME Version" header is found.

Microsoft has confirmed this to be a problem in Microsoft Exchange Server, version 5.0. This problem has been corrected in the latest U.S. Service Pack for Microsoft Exchange Server version 5.0. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):