Well, Google wants to know more and more and push their ads so their latest is (while possibly useful for some) a tad over the top for me.
I’m referring to the possibility (if you are on Google Plus) for anyone who has you in his circles to email you even without knowing your email address. To me this just opens too many possible nasty doors. Granted, if you don’t wish to answer, the sender will never know your gmail address. That won’t stop the spam, though (nor possible phishing/spear-phishing). Only by changing the settings (link below) can you do that.
So, how does one “opt out”?
Simple! Go to this address: https://mail.google.com/mail/u/0/?shva=1#settings/general
Change as in screen shot, then save (at bottom of settings page).
Source:
http://www.ghacks.net/2014/01/10/block-people-google-emailing/?_m=3n%2e0038%2e1122%2ehj0ao01hy5%2e15sh