Error message when you try to open a 2007 Office system file attachment in Outlook Web Access: "To open this attachment, you must save it to your disk"

When you try to open a 2007 Microsoft Office system file attachment by using Microsoft Office Outlook Web Access, you may receive the following error message:This problem occurs if the following conditions are true:

• The e-mail message is sent by using Outlook 2003 or by using Outlook 2007.
• You read the e-mail message in Outlook Web Access.

Note This problem does not occur if the e-mail is sent by using Outlook Express or by using Outlook Web Access.

This problem occurs because of the Exchange Server 2003 component that is used to convert the Outlook MAPI e-mail message to a MIME e-mail message type that Outlook Web Access can read. Because this component cannot recognize the new 2007 Office system file formats, you experience the problem that is described in the "Symptoms" section.

To resolve this problem, add the 2007 Office system content types to Exchange so that the conversion process can recognize these content types. A content type is a string that has a file name extension associated with it. To add the string and the associated file name extension, use Exchange System Manager. To do this, follow these steps:

1. Open Exchange System Manager.
2. Expand Global Setting Branch.
3. Right-click Internet Message Formats, and then click Properties. This operation displays the current list of known MIME content types.
4. Examine the list, and confirm that the 2007 Office system file name extensions are not in the list.
5. Click Add, and then copy and paste the appropriate MIME type from the following table in the text box that is provided. Additionally, type the appropriate file name extension that corresponds to the MIME type in the Extension check box.

   MIME type	File name extension
   application/vnd.openxmlformats-officedocument.presentationml.presentation	pptx
   application/vnd.openxmlformats-officedocument.presentationml.slide	sldx
   application/vnd.openxmlformats-officedocument.presentationml.slideshow	ppsx
   application/vnd.openxmlformats-officedocument.presentationml.template	potx
   application/vnd.openxmlformats-officedocument.spreadsheetml.sheet	xlsx
   application/vnd.openxmlformats-officedocument.spreadsheetml.template	xltx
   application/vnd.openxmlformats-officedocument.wordprocessingml.document	docx
   application/vnd.openxmlformats-officedocument.wordprocessingml.template	dotx

6. Click OK.
7. Restart the Microsoft Exchange Information Store Service to make sure that the store obtains the new list.
8. Restart Outlook, and send a new test e-mail message that includes a 2007 Office system file attachment. For comparison, send an e-mail message that contains the same attachment by using Outlook Web Access.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.