Sorry, but the so-called "bug-fix" versions proposed by Joe Feise don't work for me. I'm running TB 45 on both Mac and Windows clients. In all cases, some headers (e.g., "date" and "subject" remain blank even with the so-called "bug-fix". Looks like Mnenhy has reached the end of the road. I'm very sorry as this was one of the main reasons I moved to Thunderbird. Very disappointing.
I would be very unhappy if that were the case, but since it currently doesn't work and there have been no updates for a year and a half, I presume that it is. I've looked at the extension support page, but there is no info that leads me to believe that Mnenhy will be revived.