Marking a message as NOT spam should keep it from being put in spam folder

Emails I want keep getting put in my Spam folder. I click on them and choose "NOT Spam" and they move to my inbox but the next email from that sender goes in the Spam folder again. I know you can make rules to keep emails from being moved to the spam folder but they don't work reliably and it is not clear whether to use "move to inbox" or "keep" is the thing you want to do in the rule. Am I the only Comcast email user who thinks that if I click on an email in the Spam folder and choose "NOT Spam" that this should whitelist that sender going foreward? I am sure a lot of Comcast email users would want this and I am sure it would be very easy for the Comcast development team to add this feature.

-Don