Stefan Mileschin

Have you noticed less spam in your Gmail account? More spam? Regular e-mail being classified as spam? This is probably the reason behind the changes. Since the beginning, machine learning has helped make the Gmail spam filter more awesome. When you click the "Report spam" and "Not spam" buttons, you're not only improving your Gmail experience right then and there, you're also training Gmail's filters to identify spam vs. wanted mail in the future. Now, we are bringing the same intelligence developed for Google Search and Google Now to make the spam filter smarter in a number of ways.

http://www.hardocp.com/news/2015/07/...filter _spam/