Gmail Feature Allows Google+ Users to Email You Without Your Addres
Now, before anyone goes into a privacy panic, there are some things you should know. First, your email address still isn't visible to a Google+ connection, unless you send that person an email. Likewise, that person's email address isn't visible to you unless they send you an email.
Secondly, you're in full control over whether someone can reach you in this manner or not. There's a new setting in Gmail called "Email via Google+ in which you can determine who can send you emails via your Google+ profile. Your options are "Anyone on Google+," "Extended Circles," "Circles," and "No one." By default, the setting is configured to allow anyone on Google+ to reach your.
Google says that when someone in your circles emails you, the email will be filtered into the Primary category. If you don't have them in your circles, the email will end up in the Social category (if enabled) and they can only start subsequent conversations with you if you respond or add them to your circles.

If you don't see the setting in your Gmail account, hang tight. Google says it's rolling out to users over the next couple of days.