The practice is not well-known to users, says Microsoft. And when they find out about it, they're none to happy about it. It's hoping to damage Google's brand and maybe get some people to jump to its email service.
This isn't the first time Microsoft has made fun of Google's Gmail scanning. In 2011, at one of its salesforce events it made the video below for the audience. It's a goofy, cheesy, but decently funny spoof on Gmail.
Here's the video: