⭐ Merited by PowerGlove (1)
Didn't hard test it, so idk... Worked for my inbox/outbox. 
Well done! Ninja speed.I can only imagine what you can make when had you hard test it after good night sleep.
Just a heads-up in case you do decide to spend time on this: I'm probably going to tackle adding native PM-exporting support to SMF sometime this year. I haven't got the details fully worked-out yet, but it's likely I'll add support for multiple file-formats (mbox included) and probably look into some kind of authenticity-proving mechanism, too.
You probably won't believe this, but after noticing TryNinja posting his quick solution exporting PM's, I had a though that he should join forces with you aka PowerGlove, and that would be a true bitcointalk Power couple 
Best (public) devs this forum had ever since I joined the forum.