Email has gotten smarter over the years. Gmail suggests missing recipients and adds flights and hotel stays to Google Calendar and Google Maps. Inbox suggests short responses to emails based on their content. But in the future, as artificial intelligence becomes more powerful, the immense amount of data in your Inbox will enable much more: deeply personalized assistance.

AI has a slew of potential uses, but a large volume of training data is needed — and email is the most promising source for it. Emails contain years of personalized data that reveal our preferences in brands, food, websites, goods, services, word choice, sense of humor, and even relationships. They are transmitted across open protocols in a universal text format that enables you to grant access to any service you choose — not just those provided by a single company like Facebook.

In seconds, AI can traverse years of correspondence, bills, Amazon order confirmations, event invites, hotel confirmations, and flight bookings to learn your preferences much faster and much more thoroughly than a human assistant. And it will become continually smarter in its suggestions as it learns from both you and millions of others.

As our address books grow, so will our email client’s awareness of the people we communicate with, and not just from the emails they send. Every time we type in an email address, our clients will be able to tap into data via external services and APIs, using that information to look up data on Twitter, Facebook, LinkedIn, Yelp, and platforms not yet invented. And external services might ask for permission to use our emails to better understand us and offer us a more tailored experience outside of our client as well.

Too abstract? Here’s an example:

When I fly, I weigh travel time and cost most, but there are additional factors. You might prefer a particular airline or want to avoid a particular airport, or the availability of an aisle seat might trump everything else. In the future, AI will be able to learn from your prior bookings and airline mileage statements, and build a persona on the type of traveler you are. When you book a trip, your emails will help sort flights not by price or flight time, but by “you.” And when you book a flight, your email client will do more than receive a confirmation. It will automate filling in frequent flyer data, choose your preferred seat, and even notify you if a cheaper or better (based on your persona) flight is available within your free cancellation window. It’ll bring your boarding pass up to the top of your inbox an hour before your flight, and automatically archive it once your flight has taken off — all powered by email.

Companies are beginning to use AI to personalize your experience, but only your inbox provides insight into the companies, websites, and people that you interact with. Because of this, email will be crucial to generating the most complete, versatile, and useful applications for artificial intelligence, and we’ll finally start to unlock the full value of the messages in your inbox.