If you have a gmail.com e-mail address, and a Google+ account, pay close attention: Google has released a feature that allows anyone on Google+ who adds you to his/her circles to send you an e-mail directly, without even knowing your e-mail address.

You do not need to have these people in your circles for them to e-mail you. If they are in your circles, then their e-mails will go to your Primary tab, otherwise they’ll go to your Social tab, assuming you have the tabbed inbox feature enabled. This feature is enabled by default, even for existing gmail accounts.

Here’s how the feature works

Once someone sends you an e-mail via Google+, you have three options:

1. Allow the message and future messages by adding the person back to one of your circles, or by replying to the e-mail. NOTE: If you reply to the e-mail, your e-mail address will be made visible to the other person!
2. Block the message and future messages by clicking on the Report Spam or Abuse button.
3. Ignore the message. If you do nothing, that sender will be able to send replies to that specific e-mail, but won’t be able to send you any new e-mails in the future.

How can I opt-out of this new feature?

1. Open Gmail.
2. Click the gear-box in the top right.
3. Select Settings.
4. In the General tab, scroll down to the Email via Google+ section.
5. Click the drop-down menu and choose Anyone on Google+, Extended circles, Circles or No one. Selecting “No one” will opt you out of this feature, and you won’t see these new Google+ e-mails.
6. Click Save Changes at the bottom of the page.

There is some value to this service; maybe you live a quasi-public life, and want to allow people to contact you without necessarily making your e-mail address fully public. For these use-cases, Google should have made this feature opt-in, rather than enabled by default.