XCLN: 5.0/SP1 Macintosh Client Drops Three-Letter Extension

When you send an attachment from the Microsoft Exchange Macintosh client, version 5.0 Service Pack 1, if the client does not recognize the attachment, then the three-letter extension (if any) will not be preserved. As a result, receiving Windows clients will be unable to open the attachment from the message body. If the attachment is saved locally from a Windows client, the Save As dialog box will not have a three-letter extension on the filename.

If you manually add the correct three-letter extension to the file after saving locally from a Windows client, the file executes as expected.

Microsoft has confirmed this to be a problem in Microsoft Exchange Macintosh Client 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:

When you send an attachment from the Macintosh client, the three-letter extension (if any) is stripped off. The creator and type information of the file are examined. If there is a match in the Exchange Preferences file, Mac File Types list, then the associated three-letter extension is added. If there is no match, then the original three-letter extension is not added back, but it should be and is in the original 5.0 client.

Next, the creator and type information are stripped from the attachment and the Exchange Preferences file, Windows File Types list is checked. If the attachment is listed here, it is encoded as MacBinary2 and sent to the information store. If it is not in this list, then it is sent as Application/Octet-Stream to the information store.