We had to do a Snopes check several times with MIL. Most of the stuff she sent we could ignore or respond with a 'Wow! Those ice castles in China are really beautiful!'. That was to let her know that we were reading what she sent.
however,some were of a rather nasty nature. Those we did have to refer to Snopes because MIL had a tendancy to believe whatever certain people told her and a few of those people were likely to factually wrong and quite lurid. Every woman who goes to a certain college will be raped during her freshman year, is an example. MIL believed this and that's the sort of thing that needs correcting.
It took some time but we did get her to check things in the end.