Google's AI is writing a significant number of emails sent by users of its Inbox app.

The company's Smart Reply feature, which automatically generates email responses based on the contents of an incoming message, is now responsible for 10 percent of the mobile responses sent using the Inbox app.

The stat was revealed by Jeff Dean, senior fellow in Google's research group, who was speaking at the AI Frontiers conference in Santa Clara, California, Wednesday.

"What this does is it takes an incoming email message and then, given the text of the email message, it tries to predict what are likely responses you might want to give," Dean said. "Now, 10 percent of mobile responses on email on the Inbox product are generated with this Smart Reply feature, so it's saving people a lot of time."

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Dean didn't elaborate on just how many emails are being sent using the feature. Though not nearly as popular as the main Gmail app, Inbox has consistently ranked in the top 50 productivity apps in the App Store, according to App Annie, and the app has a significant Android following as well.

That the feature now accounts for a tenth of the app's total mobile responses is amazing when you consider that so many users are finding the AI-generated responses accurate enough to use on the go.

Google first introduced Smart Replies to Inbox in 2015, and later added the feature to its new messaging app, Allo, as well. Dean noted Wednesday that the feature also has roots in one of the company's famed April Fools' Day pranks. In 2009, the company teased a feature called Gmail Autopilot, which would respond to all your emails for you. While Smart Replies hasn't let us shed email entirely, it seems set to get a whole lot smarter.