It is not a spam filter. I just checked my "Other" after days and found a mail that was not spam but from a old friend that I had not accepted as a friend yet.

It is not a spam filter. I just checked my "Other" after days and found a mail that was not spam but from a old friend that I had not accepted as a friend yet. It is not 'detecting' spam but marking everything not-from-facebook as unimportant.