OWA saves .docx and .xlsx file as .zip

We've had a lot of complaints about OWA saving Office 2007 files using the zip extension the last few weeks. It's an old issue and I'm surprised at the number of times it's come up recently. My best guess is that a lot of organizations with Exchange 2003 are only now upgrading to Office 2007.

The problem: When any Office 2007 attachment (.docx, .xlsx, etc) is opened from OWA, the user is asked to save the document before they open it. When they do this, the default extension is .zip. If the user changes it to the correct extension before opening, the file opens correctly.

This happens because the Office 2007 MIME file types are not configured on the web server and the users browser does not know how to open the files. If IE is configured to open files based on the file header, it identifies the file as a zip, which is technically correct.

The administrator can fix it sitewide by adding the Office 2007 file types to the MIME settings on the server.

On the user side, IE has an option to open files based on content, not extension. The user should add the OWA URL to the Trusted (or Local Intranet) list and disable the option to open files based on the content. It's in IE's Tools, Internet Options, Security tab, Trusted sites (or Local Internet). It's near the bottom of the settings in the Custom level dialog.

If the administrator hasn’t updated the server and global policy prevents the user from changing the IE settings, an old Windows trick allows users to correct the extension before saving. Replace zip with the correct extension and enclose the full filename in quotes before saving it, as in this example:
"my_file.docx"

Workaround

If the administrator hasn’t updated the server and global policy prevents the user from changing the IE settings, an old Windows trick allows users to correct the extension before saving. Replace zip with the correct extension and enclose the full filename in quotes before saving it, as in this example:
"my_file.docx"

Add Office 2007 MIME types to IIS

For the sites that have not yet added the Office 2007 MIME types to the OWA server, administrators can add them in one step. Begin by stopping the IIS service then edit the metabase XML file using a text editor. The metabase XML file is at C:\WINDOWS\system32\inetsrv\MetaBase.xml.

Search for the IIsMimeMap Location element and append the following lines to the MimeMap attribute

.docm,application/vnd.ms-word.document.macroEnabled.12
.docx,application/vnd.openxmlformats-officedocument.wordprocessingml.document
.dotm,application/vnd.ms-word.template.macroEnabled.12
.dotx,application/vnd.openxmlformats-officedocument.wordprocessingml.template
.potm,application/vnd.ms-powerpoint.template.macroEnabled.12
.potx,application/vnd.openxmlformats-officedocument.presentationml.template
.ppam,application/vnd.ms-powerpoint.addin.macroEnabled.12
.ppsm,application/vnd.ms-powerpoint.slideshow.macroEnabled.12
.ppsx,application/vnd.openxmlformats-officedocument.presentationml.slideshow
.pptm,application/vnd.ms-powerpoint.presentation.macroEnabled.12
.pptx,application/vnd.openxmlformats-officedocument.presentationml.presentation
.xlam,application/vnd.ms-excel.addin.macroEnabled.12
.xlsb,application/vnd.ms-excel.sheet.binary.macroEnabled.12
.xlsm,application/vnd.ms-excel.sheet.macroEnabled.12
.xlsx,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.xltm,application/vnd.ms-excel.template.macroEnabled.12
.xltx,application/vnd.openxmlformats-officedocument.spreadsheetml.template

Open files based on Content

IE has an option to open files based on content, not the extension and this can cause issues.

First, the user needs to add the OWA URL to the Trusted (or Local Intranet) list.

Next, disable the option to open files based on the content. It's in IE's Tools, Internet Options, Security tab, Trusted sites (or Local Internet). It's near the bottom of the settings in the Custom level dialog.

For best security, do not enable this option in the Internet zone.