The engineering challenge involved in the automatic sorting of messages into categories is substantial. Google essentially has to train its computers to identify the various types of emails by signals embedded in their metadata--a task made only somewhat easier by the sheer volume of messages flowing through its platform.

Meanwhile, Mailbox co-founder and CEO Gentry Underwood says his company is strictly focused on solving the mobile email challenge.

“People aren’t trying to do the same things with mail on mobile devices as on a desktop,” he says. “When they are out and on the go, they are just trying to stay on top of their messages. So what we offer is a form of triage. You can deal with what you can and delay the rest until you can sit down and do it correctly later.”

Mailbox, which was acquired by the file-sharing company Dropbox in March, offers time-based swipe options, whereby you can choose to swipe messages right or left, “snoozing” some of them onto various lists for later use, archiving messages or deleting them.

Google says its new sorting system works on mobile platforms as well.

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Gmail Rolls Out Latest Attempt to Attack Email Clutter