Web/Android/iOS: Gmail has plenty of tools for categorising and managing your email, but that doesn't mean Gmail users feel free of email anxiety. Inbox is a new tool from Google which provides a different way of managing your mail.
One of the core concepts in Inbox is Bundles: grouping together emails on similar topics. Hence all your receipts from online shopping purchases will be grouped into a Finance bundle. You can set Inbox to only show specific bundles once a day or once a week.
Inbox clearly draws some inspiration in this area from the revamp of the main Gmail inbox last year, which automatically sorts mail into five key groups. That update wasn't popular with everyone, but the notion of automatically grouping emails based on their content can be useful (an approach also reflected in Gmail's default conversation view for emails).
An Inbox feature called Highlights automatically extracts key details from email, so you can see them without opening the mail itself. An email from an airline would show Highlights of the flight number and time, for instance. Inbox also uses this information for what it calls Assists -- useful contextual information to get something done. (Think Google Now in an email environment.)
You can also set Reminders on individual emails to be displayed at the top of your Inbox. Reminders generated by Google Now will appear here too. If you want to set an email aside for later, you can Snooze it until either a particular time or when you are in a particular location. If you want to make something off as done, you can swipe it right in the mobile apps. An automatic 'Sweep' feature pushes all emails that haven't been set as reminders or pinned off your main screen and applies the Done label to them.
Inbox is available as an Android or iOS app, and also as a webapp (though it only works in Chrome). Google stresses that Inbox isn't an alternative to Gmail; it's designed to work alongside it. Changes made in Inbox are automatically reflected in Gmail, and labels and contacts are preserved across both platforms.
Inbox is currently invitation-only. You can ask for an invitation by sending an email to [email protected]. Echoing the launch of Gmail back in 2004 (yowsah!), Inbox users will also be given invitations to share with others. We're testing it out right now and will report later in the week on what the experience is like.