We have recently gotten a lot of complaints from users who say that we are blocking their attachments even though it is not on the list of attachments we say that we block. After a little investigation we found that these users had installed an Outlook plug-in that automatically zips all file attachments. Since the user didn't realize that they were sending a .zip they complained that our filters were broken.
The software that we have seen is Quick View Plus and is available from the site below.
http://www.avantstar.com/stellent/intradoc-cgi/idc_cgi_isapi.dll?IdcService=SS_GET_PAGE&ssDocName=QuickViewPlusFeatures
It shows up in the Add-In Viewer (Tools -> Options -> Other -> Advanced Options -> Add-In Manager) as something like CommView Plus Auto Zip Extension
