I use an alternate spam filter process. I use a "+" sign in my gmail address. So I would subscribe to a promotion/giveaway with username+company@gmail.com. This is a great way to catch which promotion/company sells your email address to unwanted companies.

Caveat, sometimes an unsubscribe website can't handle the "+" symbol in an email and you'll continue to get spam. So, just add a filter for that "TO" email to forward to the spam/trash folder.