www.BlackViper.com: E-Mail Filtering Guide

Image 2.7

15) This filter passes any other E-Mails that do not meet any previous rules to the SPAM folder. (Image 2.7)

If this was not here, it would place those E-Mails in the "Inbox," but I really do not like that as I highly doubt that any "legit" E-Mail would pass through my filters and NOT be spam.