Fortunately, your email address will not be displayed, just your name. However, once that person emails you and you respond back, they will then be able to see your email address. If you don’t want this happening, there’s an easy way to fix it in Gmail’s settings.
To go directly to the General Settings page, simply click this link. Scroll down until you see the “Email via Google+” section. You’ll notice that by default it’s set to “Anyone on Google+.” From the drop-down menu, you can change it to Extended Circles, Circles, or No One. Unfortunately, there’s currently no way to choose specific circles; it’s either all or none. Once you’re done, don’t forget to scroll down to the bottom of the page and click “Save Changes.”
There you have it. Now, you don’t have to worry about just any Google Plus user emailing you. What do you think of this new Gmail feature? via Official Gmail Blog