Google is today making a change to Gmail that will further bake in Google+ to its webmail product in a way that’s actually somewhat practical, though also potentially invasive. Going forward, you’ll now be able to directly email your Google+ contacts from Gmail, even if you don’t know their email address. And by default, anyone on Google+ will be able to email you as well, thanks to this new option, if you don’t adjust your settings.

This feature appears as you begin typing your contact’s name in the “To” field of an email message. Matching contacts display first at the top of the list of suggestions provided by Gmail’s autocomplete, while your Google+ connections appear below.

Because of the privacy implications of this feature — and the possibility of overwhelming the inboxes of more public figures — Google has at least put controls in place that allow you to specify who can send you emails.

You can choose from “No one” to continue on as normally, or open things up a bit wider by choosing from “Circles,” “Extended Circles,” or even “Anyone on Google+.” And of course, because Google+ is now the default platform for YouTube commenting, and required for things like setting up a new Gmail account, the “Anyone on Google+” option is much larger today than in earlier years. Many people are technically “on Google+,” even if they aren’t active on the Google+ destination site itself.

In addition, Google explains that not only are you able to specify who can send you emails, your email address isn’t visible to a Google+ connection until you send that person an email, nor is their email visible to you, unless they send you an email.

The feature also takes advantage of Gmail’s previously introduced tabbed interface, which breaks the Gmail inbox into sections like “Primary,” “Social,” Promotions,” and more. Going forward, emails from those in your Google+ Circles will appear in the “Primary” section, while those you don’t have in your Circles will be filtered over to the “Social” tab instead. Those users will only be able to start a conversation with you if you respond to them or add them to your Google+ Circles – something you can do right from the email header (which fortunately offers a visible “Report Spam or Abuse” link, as well).

This new feature is an expansion on the Google+ integrations the company first introduced back in late 2011 which originally brought Google+ to the Gmail inbox and Contacts section. The addition allowed users to automatically update their address book with a contact’s most recent information, making Google+ a more practical service than before. Also at the time, Google added a widget to the Gmail sidebar for viewing a contact’s most recent Google+ post, allowing you to add them to your Google+ Circles.

Like before, the newer integrations are practical and useful when you need them as a sender, but could be disruptive to you as a recipient of emails — much like email itself, if you think about it. For those who still use the “Priority Inbox” interface instead of tabs, the additional emails could become cumbersome. But Google is making the setting available to users before the feature launches, so they’ll be able to at least adjust their settings before a deluge occurs. (Unless, of course, they get so much email that they miss the note from Google.)

Google says the new feature is rolling out over the next couple of days to everyone who uses Gmail and Google+. Users will be alerted by way of a link to the setting when the feature is available to them.