Comment 99 for bug 490935

(In reply to Lee_Dailey from comment #85)
> this extension from paolo kaosmos does the job. it replaces the old
> headertools extension mentioned in comment 37 and is actively supported.
> - Headers ToolsLight: edit Subject, Sender, Full source etc
> [Forum] http://forums.mozillazine.org/viewtopic.php?f=28&t=2300561
> it seems like a good workaround until tbird finally includes the ability.

The addon can be downloaded from here (reported to work with TB24, and actively maintained):

https://addons.mozilla.org/de/thunderbird/addon/header-tools-lite/