Unfortunately Microsoft Email servers still to this day send emails out in the proprietary TNEF format (We see this as a plain text email with a winmail.dat attachment). The Lookout (fix version) add-on decodes this attachment so you may open the attached files.
I've just published the V2.0.00 for the Thunderbird plugin Lookout (fix Version). This is an update for the coming versions of Thunderbird that significantly change how addons are implemented.
There are some known visual glitches and the debugging logs currently do not work, however attachments should de-code and save as expected. I would appreciate any testers to give it a shot.