Google wants to make email easier to use on mobile devices, as is clear from Inbox--an interface for viewing existing Gmail accounts primarily on new iOS and Android apps.

Unfortunately some of Inbox's functionality competes with the efforts of major airline, hotel, and car rental companies to "control the conversation" with their customers via their branded apps or email marketing messages.

Launched this quarter, Inbox is technically an experiment that is open on an invitation-only basis. But requesting an invite is easy through the Inbox website.

Inbox itself may or may not catch on with users. But the app illustrates Google's intent in making its mobile apps act more like personal assistants. This affects travel, in particular.

Google wants its own interfaces to be the main portal through which users view their trips, check in for flights, keep tabs on flight status, and make dinner reservations at their destination.

Bundling

Inbox automatically sorts, or bundles, relevant emails into categories. It does this more aggressively than Gmail's recent introduction of sorting mail into "Promotion" and "Social" tabs.

"Travel" is the first default category in Inbox. All travel-themed emails, such as Zipcar reservations and Airbnb bookings, are automatically moved to this bundle. (Users can tweak the app's settings, of course.)

Inbox's search functionality is superior to Gmail's in that if you type the word "flight" into the search box, it will show you a "card" displaying the booking details of your upcoming flights.

The overall Inbox intention with travel is to break users' habits of hunting through several old emails to find relevant trip details, itinerary information, and boarding passes.

Inbox instead enables users to create "Reminders"--little cards that pull out the bites of relevant information from emails and push them to the top of the screen, as needed.

To use a travel example, a user can set an Inbox Reminder to be prompted to make dinner reservations. The Reminder can pull the hours the restaurant is open and the number to call it from Google's search engine and push it to the top of the mobile device's screen.

In the case of an upcoming flight, a Reminder message will pull flight status information--something that's not in the original message--and display it in a "Highlights" card.

Inbox isn't Google's only effort to pull out travel information and make trip details more relevant to users.

For instance, as of this month, if you have Google's newly revamped Calendar app (Android-only, for now), flight reservations are automatically added to your calendar. The details stay updated in real-time, such as if your flight is delayed.

Google's multiple-front war for users' attention on mobile may affect the travel industry more than other industries because of the real-time, often spontaneous, nature of its product.

To respond, travel brands may become even more creative with alternative ways to keep customers interested in their branded interfaces by providing features Google can't copy.

A case in point: In November, Starwood said it was adding keyless entry via its mobile apps for ten properties in the US.