Google has refreshed its terms of service, explicitly stating for the first time that it scans the contents of users' emails to target them with tailored advertising.
The clarification in its terms follow recent legal challenges to Google over its handling of email and Microsoft's recent Scroogled campaign, which draws attention to Google's email-scanning practices.
Google's terms, updated on Monday, state: "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."
Google's previous update in November 2013 outlined that it may use Google Account holders' profile names, photos, and actions, to help with displaying ads and for other commercial purposes.
"We want our policies to be simple and easy for users to understand. These changes will give people even greater clarity and are based on feedback we've received over the last few months," a Google spokesperson told ZDNet in a statement.
Last month, US District Judge Lucy Koh knocked back a class action claim that attempted to combine a number of separate complaints, filed earlier, that accused Google of breaching US wiretap laws over its email content scanning. The plaintiffs were also prevented from pursuing the class action again in future.
While the ruling was a major win for Google, last year Koh rejected the company's argument that all email users implicitly consented to interception because of "the way that email operates".
Microsoft has honed in Google's email scanning to mark the differences between Gmail and Outlook as the Redmond company attempts to bring back users to its webmail service.
In March, the UK's advertising watchdog rejected two complaints that Microsoft's Scroogled radio ad campaign was misleading. In the ad, Microsoft claimed it didn't scan email, even though it does do so in order to detect malware and spam.
The challenge was defeated on the grounds that it could be understood in the ad that Microsoft was only referring to scanning in the context of advertising, whereas it was accepted and expected that companies would do protective scanning.