Show the Sender header in the message pane
Carsten N. from JonDos suggested that we set mailnews.headers.showSender to true; doing this will show the Sender header in the message pane.
In a nutshell: setting this to true can help enhance X509 certificate validation where an attacker may use a fake From header. This is not a complete solution but it may help attacks described in the article http://heise.de/-2044405.
It was also suggested to make this a default option in Thunderbird. https://bugzilla.mozilla.org/show_bug.cgi?id=332639
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