Recently Gmail announced a feature which enables Google+ users to email you on your Gmail id (if you are a user of both Google+ and Gmail).
For those who do not like this new feature, we have figured out a setting to stop random people emailing you.
Here is what you have to do.
1) Click on the Gear icon at the top right hand corner of your Gmail account, select the settings option.
2) Go to the General tab, navigate to the Email via Google+ section. In the “Who can email you via your Google+ profile?” select the No one option from the drop down list.
3) Navigate to the bottom of the page and click “Save Changes”.
And you are done.
The good part is that your email id is not shared with people until you reply to them. This feature is not yet activated for some people but is in the process of being rolled out.