xlsx files are being interpreted as zip files on download, why?

Solution 1:

You can indeed fix this in Apache's configuration. Add the following lines (and ensure that mod_mime is enabled):

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

This will ensure that Apache sends the appropriate MIME type to the client, and IE will understand that the files are Office documents and not zips.

Solution 2:

I doubt it's an apache config issue. Internet Explorer has it's own MIME Type Detection algorithm. You can circumvent this behavior by right-clicking and selecting 'File -> Save As' or just use MS 2003 .doc format.

Solution 3:

if its an apache config issue then there is the file that contains the mapping of extensions to mime types that you can quickly examine to rule out this possibility.