DOCX Extension file uploads

I am not very sure if this should go to Mime Detect or file field module's issue queue?

Well, here is the issue
I know drupal provides mime detect module which actually uses unix file command and you integrate to that. My problem is with office 2007 file extensions.

for example I may allow docx in file field but the files are actually zip files. so it does not work.

I changed .htaccess in the core , httpd.conf and also mime.type in linux to include docx extensions but no avail. I just wondered how do we fix this problem?

Thanks