Mozilla Thunderbird 15 has the option of “Do not track” associated with it. What this means is that when this feature is turned on, there will be an opt-out from various advertising and media networks which display targeted ads.
By default, Do Not Track is off in Thunderbird 15. To enable it :
Go to Preferences > Preferences by clicking the three row icon on far right.
Go to “Security” tab and under the “Web Content” section, enable the option “Tell websites I do not want to be tracked”. Hit Close when done.
By the way, to turn on the Do Not Track feature in Mozilla Firefox, please refer to this earlier post.