Google announced a new Gmail feature that lets anyone with an account on Google+ send you an email. While you can’t see email addresses unless someone sends you an email, and vice versa, you can still contact people with a Google+ account by selecting their profile from an auto-complete drop down menu when you compose an email.
By default, Google will allow anyone to email you. You'll be able to change that setting within Gmail to allow email via Google+ only from your extended circles (i.e., friends of friends), just your circles, or no one.
A Google spokesperson told me that the company will be alerting Google+ users to the new feature via email, and that it won't be active until all those emails have gone out. What's more, people who don't know you—that is, who aren't in any of your circles—will only be able to contact you once unless you reply or add them to one or more circles.
The company said it will roll out the feature over the next couple of days.
The new feature also takes advantage of the new Gmail inbox buckets that Google announced back in May. When someone in your circles emails you, the conversation will appear in the “Primary” tab. If you don’t have them in your circles, their messages will be filtered into “Social.”
This is the latest push to deeply integrate Google’s not-so-social network across all platforms. Last year, the company implemented Google+ on YouTube, forcing all commenters to first sign up for a Google+ account.