when looking into a regular folder, it can be useful to look at the list of intended primary recipients instead of the senders, and while in the "Sent" folder it can be useful to look at the From: as well.
This plugin adds a link to toggle the displayed column (From or To).
It has been tested on 1.4.15; however it should work with other 1.4.x versions as well. please report me if it works with other versions
the plugin