Gmail update: Reach more people you know
How it works with email addresses
Emailing Google+ connections works a bit differently to protect the privacy of email addresses. Your email address isn't visible to your Google+ connections until you send them an email, and their email addresses are not visible to you until they respond.
How to control who can contact you
You're in control of whether people can reach you with a new setting in Gmail on the desktop. To learn more, check out the Help Center.