Google Now Allows Anyone on Google+ to Email Your Gmail without Your Address, Here’s How to Disallow That
Is this some kind of deliberate test of their spam filters?
The latest in a series of changes, Google has allowed anyone on Google+ to send emails to Gmail accounts. It's OK, though. There's a solution that does not involve hiding from your email for the rest of your life to avoid spam. Like the recent change to image display settings, the Google+ email feature is easily turned off.