Comment by grepular

DNS pre-fetching was disabled in v3.0.2 - https://bugzilla.mozilla.org/show_bug.cgi?id=544745#c21

I am surprised that you're seeing leaks in Thunderbird 10.0.2. That is my own client of choice so I'm always keeping an eye on it after updates and I am not currently seeing any leaks... If you have remote images disabled, are you still seeing leaks? If so, which ones?