By tech editor Ian Bush

REDMOND, Wash. (CBS) — Microsoft is going on the offensive against the world’s most popular e-mail service, starting a multimillion dollar advertising blitz that questions the way Google makes Gmail free.

Microsoft is pushing its Hotmail successor, outlook.com, with an advertising campaign targeting the ads that Google displays alongside its e-mails.

(advertisement audio:) “…Google crosses the line and goes through every single Gmail — every word, in every email — to and from everyone, to sell ads based on your most personal messages.”

“You get ‘scroogled’ when your privacy is invaded,” the ad says.

Most free e-mail services are supported by ads.  Google says it uses software, not humans, to tailor ads based on e-mail content.  In addition, Gmail allows its users to remove the ad personalization, replacing targeted ads with generic, universal ones.

Microsoft put up a petition (at scroogled.com), hoping for public pressure to get Google to change the way it does business.

Microsoft also scans e-mails — for viruses, or to mark them as spam.  Outlook.com ads are based on the web sites users visit, rather than the message content.

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