Photo: Google says incoming and outgoing emails are analysed for advertising purposes. (Clay McLachlan: Reuters)Related Story: Google fined $22m for Safari privacy breach
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Google has updated its terms of service, explaining to users that their incoming and outgoing emails are automatically analysed by software to create targeted ads.
The revisions more explicitly spell out the manner in which Google software scans users' emails, both when messages are stored on Google's servers and when they are in transit.
It is a controversial practice that has been at the heart of litigation.
Last month, a US judge decided not to combine several lawsuits that accused Google of violating the privacy rights of hundreds of millions of email users into a single class action.
Users of Google's Gmail email service have accused the company of violating US federal and state privacy and wire-tapping laws by scanning their messages in order to compile secret profiles and target advertising.
Google has argued that users implicitly consented to its activity, recognising it as part of the email delivery process.
Google's updated terms of service added a paragraph stating that "our automated systems analyse your content (including emails) to provide you personally relevant product features, such as customised search results, tailored advertising, and spam and malware detection. This analysis occurs as the content is sent, received, and when it is stored".