Google searches every word in your mail before it reached to your inbox.
that's the part now Microsoft is aiming to notify.
Now they came with full site and analysis.. http://www.scroogled.com/
What Google does in mail..??
Google scans every word in every mail and offers small advertisements that are related to the content in the mail.
It takes keywords in the mail and populates the ads instantly, that's how they make money.
Why and how Microsoft is making a note about that?
Microsoft also launched Hotmail services long back before Google, and Google take the leadership of the web-based free mail service.
To take control of the situation Microsoft started/converted it's new mail services through Outlook.com. Now it want to spread through different marketing.
Microsoft is gaining users with the help of windows 8, Sky Drive.
Google is gaining the users with the help of it's most popular android devices, and it's many services viz, Google Drive, YouTube. Google has 452 million users and Hotmail has 325 million active users.
Microsoft now prepared full presentation in it's new web site Scroogled.
What Google is saying about their strategy of giving relevant ads?
Google is giving explanation that it is using it for the right purposes and giving you for the chance of better experience.
It's all depend on the user perspective to use the mail. If you are a business man you probably not using Google since you won't wish to read anything in mail. It doesn't mean that personal users don't have secrets. If you don't accept the fact that Google is making money from your mail and not giving money to you :P, then you definitely change the mail to Outlook.com. If you don't even consider this, it all looks silly.