funny thing about that, some time ago I tried to figure out how to stop all messages from fbook to my email, after menu hopping for some time, I allowed my gf to go into the settings and turn it all off and turn on many privacy settings. I know fbook has changed the privacy things several times since then, but I don't use it enough to have any issues I think.. I also don't use messenger app or fbook mobile, so I've gotten lucky (and helped) to get zero messages from them for years.