Google is changing the relationship between Gmail and Google+ by allowing people to email you directly without knowing your email address.
The change, which is rolling out from today, gives you a new option in settings called 'Email via Google+' where you can choose who can email you -- people you follow in your circles, people who are in the circles of people in your circles, anyone on Google+, or no one at all.
By default, it's set to 'Anyone on Google+', although I'm seeing reports that if you have a large number of followers the default may be 'Circles'. If someone emails you via Google+ in this way, they don't see your email address, however.
I haven't had the change roll out to my profile, either work or personal, but Google says it will send you an email when it happens -- although some users who contacted me after reading this story earlier did not receive this email.
How to change it to 'no one'
You can stop it happening by clicking the gear icon, going to settings and finding Email via Google+ in the first General tab. A drop-down box will let you select the setting you want.
"Have you ever started typing an email to someone only to realize halfway through the draft that you haven't actually exchanged email addresses?" Gmail product manager David Nachum writes on the Official Gmail Blog. "If you are nodding your head 'yes' and already have a Google+ profile, then you're in luck, because now it's easier for people using Gmail and Google+ to connect over email."
Gmail will also suggest Google+ contacts as recipients when you're writing an email -- the ones who've not opted out, that is.
Google's new category filters are used to separate people you follow with those you don't. "When someone in your circles emails you, the email will appear in the Primary category," Nachum explains. "But if you don't have them in your circles, it will be filtered into the Social category (if enabled) and they'll only be able start another conversation with you if you respond or add them to your circles."
I contacted Google for comment, but a spokesperson said it had nothing to add beyond Nachum's blog post.
The software behemoth attracted widespread opprobrium last year when it. While it seems logical for the company to use its most popular services to give its social network a leg up, it's not always in the best interests of its users.
Have you seen the change on your profile yet? Do you think it's a useful addition to Gmail, or a bit of an imposition? Send me a message in the comments, or on our unintrusive Facebook page.
Update: A previous version of this story stated that the default was intended to be 'Circles'. This is not the case.