It's no secret that Google has been working hard to push its social network into the mainstream. Google has killed off some of its own products — e.g, the late Google Reader — in an attempt to drive more users into the arms of Google+. A more common tactic, however, has been to create bridges between the social network and other popular Google products.

Google has connected YouTube comments to Google+ posts (for which we are eternally grateful), but has also connected Google+ to Gmail in various ways, which may not sound as inviting. But rest assured, most of it is not mandatory.

If you're not aware of these connections yet, here's everything you need to know about what they mean for you, and how you can opt out.

Send & Receive Emails From Your Google+ Contacts

This is perhaps the most significant Google+ integration currently out there: you can send and receive emails to and from your Google+ contacts, without actually sharing your email addresses with one another. So how does it work?

If you choose to enable the feature, as you're composing an email, it should show you your Google+ contacts as possible recipients. If they reply to you, only then will you actually have their email address, and of course by emailing them, you're sharing your email address with them.

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How To Opt Out

While this might sound like a huge privacy nightmare, it is an entirely optional feature. If you'd like to opt-out of receiving emails from your Google+ contacts, just head over to your Gmail settings and disable it. You'll find it under the 'General' tab, labeled: Email via Google+.

You can allow anyone on Google+ to email you or restrict the feature to only people in your circles, people in your extended circles (i.e., friends of friends), or to no one at all.

Settings

View Google+ Profiles in Gmail

In 2011, Google announced the first connections between Google+ and its email behemoth, introducing content from your Google+ profile alongside emails you've sent. So regardless of whether or not you're connected to someone on Google+, they will see your latest public post in a sidebar to the right of your email. They can click on your most recent posts or photos and add you to their circles directly from Gmail. 

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How To Opt Out

While this may not be as intrusive as the latest addition, it does mean you'll want to be aware of what you're posting on Google+, knowing that it can be viewed by anyone you email with a Gmail address.

While there is no way to 'opt-out' per se, you can be selective about what you share publicly on Google+. The content viewed in Gmail is either content you have shared publicly on Google+, or, if the person is already in your circles, content you have shared to your Google+ connections. So just remember to be mindful about the kinds of things shared on social media.

Filter Emails by Google+ Circles

An incredibly useful (and non-intrusive) way in which Google has connected its email and social network is by allowing you to easily filter emails, to view only those sent to you by people in your circles.

In the sidebar on the left, you can select specific circles, which if you've carefully crafted, offers you an easy way to find emails from very specific people. This feature is not something that requires an opt-out option, but you can choose to show or hide it in your label list.

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Update Contact Information Automatically

If you update your own contact information in Google+, it will automatically update your contact information saved in other people's Gmail address books. So if someone has your contact information in their Gmail account, and you're connected on Google+, you should know that you're automatically sharing new contact information with them.

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It's also worth noting that if you have publicly posted your contact information on Google+, it can be viewed in Gmail, not only by people you've added to your circles, but also by people who have added you to their circles.

How To Opt Out

Your contact information will only be shared with your Google+ contacts through Gmail, if you have already publicly shared your new contact information on Google+ itself. If you've done this, there's no way you can prevent others from seeing your contact information on Gmail.

What do you think of Google's attempts to connect Gmail and Google+? Useful or an invasion of privacy? Let us know in the comments.