Google has caused a privacy stir yet again, as Gmail contact lists will now include both the email addresses of their existing contacts, as well as the names of people on the Google+ social network.
The move could result in some users receiving messages from people with whom they have not shared their email addresses, raising concerns among some privacy advocates.
Google is increasingly trying to integrate its Google+, a two-and-a-half-year old social network that has 540 million active users, with its other services.
When consumers sign up for Gmail, the company's Web-based email service, they are now automatically given a Google+ account.
Google said the new feature will make it easier for people who use both services to communicate with their friends.
"Have you ever started typing an email to someone only to realize halfway through the draft that you haven't actually exchanged email addresses?" the company said in a blog post announcing the feature. "You're in luck, because now it's easier for people using Gmail and Google+ to connect over email."
Google said that users who did not wish to receive email messages from other people on Google+ could switch the settings so that they receive messages only from people they have added to their networks of friends or from no one at all.