Voir aussi :
http://www.brighthub.com/office/collaboration/articles/71421.aspx
XNote++
To avoid leaking your locale you should change the mailnews.reply_header_authorwrotesingle and mailnews.reply_header_ondateauthorwrote fields to be the same as in this example.
If you can not change the timezone on your node to GMT then you should also set mailnews.reply_header_type to 1 instead of the default which will cause it to only refer to the author and not the time they wrote their message, otherwise Thunderbird will leak your timezone.
If you can change the timezone on your computer (running in a VM helps here) then you should set it to GMT and can leave the header type set at 2.