Spam Blocking

Over the past year the spam blocking for my Comcast account has been next to useless.  I'm constantly getting spam delivered to my inbox while at the same time getting mail that I keep clicking "not spam" for keeps being delivered to my spam folder.  Anything from Steam and Amazon is sent to spam even though I click the NOT SPAM button.  I've also tried setting up filter rules to deliver any email from them to my inbox but it doesn't change anything.