After I moved my web site to a new host, one of the things I set up was for one email address to be a catch all.
Once that was set, I found that someone has been using the domain when setting up facebook accounts. Lots and lots of facebook accounts with a female first names.
I'm not sure what the point is. As far as I can tell, the accounts can't be used, you need to confirm the email address with facebook before the account can be used.
So, the domain will now bounce any such messages back to facebook. They aren't valid and they aren't useful.