The feature is based off an idea from Gmail engineer Bálint Miklós, Google said in a 2015 blog post. Miklós asked the Google Research team if there was any way to create some tappable template replies in Gmail. There are, after all, plenty of emails to which one could respond with just a "Got it," "Thanks," or "See you soon!" Having some pre-made responses at one's fingertips would save everyone a little more time, Miklós thought.
-- Why am I seeing this now?
Google users have had access to this feature since 2015, but only in Google's smaller and more experimental Inbox app. And the suggestions offered by the feature have been getting steadily more advanced as it's learned from the decisions of more customers. Based on that success, Google has decided it was ready for more general use.
-- How does it work?
Smart Reply relies on machine learning to scan the subject line and body of an email and make suggestions based on what it sees. The company said it has built up a huge bank of anonymized customer messages and response decisions to help accomplish this.
It is also designed to remember your individual preferences for things, such as punctuation. So it will be able to adjust its suggestions depending on whether you're a "Thanks!" or "Thanks." type of person.
Smart Replies won't appear on every email though, Google said. You're most likely to see response suggestions on emails that can be easily answered with a simple sentence or two.
-- So...is someone at Google reading my email?
There is no person at Google reading your email, according to Google. Even when research scientists were building the feature and trying to suss out which responses matched which messages, they designed their testing to make sure that no person ever read a Gmail user's email.
But it does mean that Google's software is scanning your messages, much in the same way that its spell-checkers and spam filters do right now. Google anonymizes all the data from these tools, but the fact that your messages are being scanned is still worth noting.
-- Can I turn if off?
Yes. You are able to turn off Smart Reply through your settings menu.
-- How well does it work?
Smart Reply suggestions have been getting steadily better as the feature has matured and learned from users' decisions. But it's still not perfect. Language, after all, is a complicated thing. Google researchers Brian Strope and Ray Kurzweil wrote about how difficult it is to parse the sentence, "That interesting person at the cafe we like gave me a glance," in a blog post this week.