I've been using Thunderbird for about 2 years and this problem has only started recently. Currently on 31.5.0 and Firefox 36.0.4 on a MacBook Pro. For some reason, every time I *open* an email attachment to view it, Thunderbird automatically *saves* it to my Desktop whether I want to or not. In Preferences>Attachments I have it set to "Always ask me where to save files" (see attached). It's always been that way. Just because I may view an email attachment doesn't mean I necessarily want it saved. I know I can change the destination folder to something other than Desktop, but what if I don't want to save an email attachment at all...how do I stop it? Can't find a solution anywhere on the web even though I've seen the question raised by others over several years.