Yup .. I have had to give a couple of clients bad news now with this one. Be aware it is also network aware and will encrypt mapped drives as well (NAS box, home server, etc). If you have a larger network you can always create a group policy object stopping users being able to execute files from the temp location. This helps get rid of the clickety click problems but means you actually have to save the attachment that you want to open.
Just think before opening any attachment like this "how does this company know my email address to send me this thing? "