Hi,I wondered if anyone else has seen this.We upgraded to Office 2007 and immediately had problems with attachments. I followed a guide to add the various formats in System Manager | Global Settings | Internet Message Formatsie application/vnd.openxmlformats-officedocument.wordprocessingml.document docx This appeared to work fine but then over the next few weeks we noticed users still having problems with some attachments. I know if they forward an old attachment that was sent before the changes then they will still have problems but they shouldn't if they attached it after the changes.I had a pupil who wrote a docx file last week and sent it to himself using OWA and then here in school today he gets the "To open this attachment, you must save it to your disk." error. I got him to send the message to me and sure enough I get the same problem. If I save the file and re-send it back to him as a new attachment it works fine. Any ideas what could be causing this? We are using Exchange 2003 SP2 on a Windows Server 2003 Standard Edition SP2 server.

Hi, The first time you try to open an attachment with OWA it looks for the MIMETYPE to see if it is permitted. If the attachment MIMETYPE is listed in the Level2MIMETYPES or the attachment extension is listed in the Level2FileTypes, the issue will occur. Level2MIMETYPES specifies a set of MIME types that are potentially dangerous as attachments. Attachments matching this type will not be opened automatically but rather a dialog will be presented to the user asking them to save the attachment locally on their server or machine first. Then the user can open it. To resolve the issue, we need to change the value for the Level2MIMETypes in the following registry: 1, Open the registry 2, Locate to the following key: HKLM\system\currentcontrolset\services\msexchangeweb\owa 3, Then find the value of Level2MIMETypes. 4, Please remove application/octet-stream there. 5, Test the issue again. Related KB article: 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" http://support.microsoft.com/kb/952770 Hope this helps. Thanks, Elvis