I am so sick of getting unwanted mails in my gmail inbox that I am now willing to create a white-list kind of extension which filters all mails coming from people who are ***not*** in my contacts list. I searched for this many hours but could not find anything hence thinking of doing this exercise (if it exists, please share the link). I have created 100's of filters but definitely spammers outpace me everytime.

Can someone tell me whether this is possible in first place? I have seen extensions which add functionality in gmail but I don't know how to block an email through an extension. Plz help.