Google has updated their privacy policies making it completely clear that they are scanning your email. Here is what was added:
Our automated systems analyze your content (including emails) to provide you personally relevant product features, such as customized search results, tailored advertising, and spam and malware detection. This analysis occurs as the content is sent, received, and when it is stored.
When you upload,
or otherwisesubmit, content to our Services, you give Google (and those we work with) a worldwide license to use, host, store, reproduce, modify, create derivative works (such as those resulting from translations, adaptations or other changes we make so that your content works better with our Services), communicate, publish, publicly perform, publicly display and distribute such content.
Would you still use gmail after knowing this? Make some noise in the comments below!