Google sent me an email today announcing that Google+ users can now send emails directly to my Gmail inbox if I'm in one of their Google+ circles, even if they don't know my email address. I only want to receive emails from people I've explicitly given my address to. Is there any way to disable this "functionality"?
Yes, this can be disabled, but it is enabled by default.
If you go to the main Gmail settings page (on the general tab), there is a setting (about 9th from the top) for "Email via Google+". You can choose from the following options:
- Anyone on Google+
- Extended Circles
- No one
"Extended circles" means that the user is in the circles of one or more people who are in your circles, but they are not directly in your circles. It's like the "friends of friends" option on Facebook.
For more information, see the full Gmail Blog post on it.