Photo

Google will soon allow people to send anyone an email, even if they do not have the person’s email address, as long as both people have a Gmail and Google Plus account.

The change, which was announced Thursday and will be introduced over the next few days, was met with protest by some Gmail users, who said it opened the door to spam and unwanted solicitations in personal email inboxes, which are considered private.

Google said the new capability would be useful for people who know one another but have not yet exchanged email addresses.

Senders can email anyone as long as they follow them on Google Plus, which they are able to do without permission. Recipients can receive email from anyone on Google Plus. Their email address only shows up, though, if they reply to the email.

The ability for anyone on Google Plus to email a Gmail user will be automatically turned on, requiring people to opt out if they do not want to be reachable. Gmail users can turn it off by visiting the General tab on the Gmail Settings page, where they can choose to receive email from anyone on Google Plus, people in their circles or extended circles or no one.

Google plans to send emails to Gmail users explaining the change before turning it on. Emails received from people outside a Google Plus user’s circles will be filtered into the social tab in Gmail. The default setting for business Gmail accounts is turned off.

The change, which more tightly integrates Gmail with Google Plus, is the latest move by Google to weave its social network into all of its products and to strongly push users to sign up for Google Plus. It comes on the heels of an uproar by many YouTube users after Google required people to join Google Plus to comment on YouTube videos.

Google has grappled before with the gulf between ideas conceived by engineers and the desires and concerns of its users.

For instance, the change is reminiscent of the set-up of Buzz, the social network based on Gmail contacts that Google started in 2010. Buzz was met with an uproar and was the subject of a Federal Trade Communications fine over privacy violations, before being shut down.

Buzz, like the new Google Plus email feature, was turned on by default and required people to opt out if they did not want their Gmail inbox linked with a social network.