Free E-Mail With a Steep Price?: Here’s the agenda behind GMail. You knew there had to be a catch.
Google said it would use automated technology to scan the content of incoming e-mail for keywords and place related text ads inside the mail. For example, if someone sent an e-mail to a Gmail user suggesting they go out for Mexican food, the recipient might see a couple of text ads in the right column of the e-mail suggesting specific Mexican restaurants in their area.