Google on Friday introduced vital changes in Gmail and Google+. Now any user can send mail to other user without actually knowing their email address. This means a user can get a mail from people not in your address book and this mail will land in your Social category but not the main inbox.

This mailing options works a bit differently so that your email address is only shared with the people you want. Your email address won't be visible to a Google+ connection unless you send that person an email, and likewise, that person's email address won't be visible to you unless they send you an email. Also user can opt out of this option if they like but in terms of privacy, a scared user will definitely go for it.

Google product manager David Nachum said, “Have you ever started typing an email to someone only to realize halfway through the draft that you haven't actually exchanged email addresses? If you are nodding your head 'yes' and already have a Google+ profile, then you're in luck, because now.”