what exactly his Facebook email address is? Then there's no need for you to guess.
And it might be a suggestion for him to make a rule in hotmail that automatically forwards all mails received to his own facebook email. If only for people like you.
I personally have issues with Facebook. Not so much all the privacy invasion issues (though those are valid concerns), really what bugs me is the idea of having a dozen email/social-networking/messaging services. I would love to be able to do it all from Gmail, and that's all. The problem is that a lot of my friends now check their Facebook exclusively. If I send something to their hotmail it might take them 3 weeks to answer, but they check their Facebook 3 times in a day.
I heard that I can send emails to their @facebook.com address, and the message would pop up in their message feed. But I've tried (from my gmail) and none of my messages go through. To use a fictitious example, to send a message to my friend's "John Smith" Facebook account. I typed up, John.Smith@facebook.com and sent him an email. He never got it. I also tried email@example.com, still no luck.
I know there was recently an account email reshuffle or something at Facebook, but I'm not familiar with the details. Any help would be greatly appreciated.