Most of us are desperate to spend less time in our email inboxes, but the influx of messages keeps us battling for Inbox Zero. But what if someone told you the key to email efficiency was spending more time in your inbox? That’s the premise behind PowerInbox, a Cambridge startup that integrates apps into email, which today launched its API.

The new API will allow companies to develop apps to integrate their products and services with email messages, allowing them to use the medium not just to drive traffic, but actual engagement.

“Until today, people interacted with emails by hitting reply or forward, or by clicking on URLs to launch webpages – taking you outside the context of email,” explained Matt Thazhmon, founder and CEO of PowerInbox. “All this back-and-forth drains productivity and effectiveness. PowerInbox lets people stay where interaction begins – inside emails.”

With PowerInbox, if you get a follower notification from Twitter you can follow back right from your email interface rather than clicking and going to an external site. Ditto with Facebook commenting and number of other services. With the launch of its API, PowerInbox hopes to expand those offerings dramatically.

The company claims to boost email click rates from the typical 3-4% to 30% with its service.

PowerInbox currently supports Gmail, Hotmail, and Yahoo Mail for both Chrome and Firefox users, and expects to add Outlook, Thunderbird, Safari, and Internet Explorer later this year.

Here’s the list of PowerInbox API launch partners:

  • Followup.cc: Enables one-click snoozing of emails for later review.
  • Fundraise: Allows donations inside emails.
  • NextWidgets: Browse store items inside emails.
  • OmniStrat: Enables response to SocialStrat panel activity within emails.
  • Senexx: Facilitates construction of enterprise knowledge inside emails.
  • Smak: Enables interacting with relationship alerts inside emails.
  • Symbyoz: Connect with your network inside emails.
  • TimeTrade: Schedule meetings within emails.
  • TumbleCube: Enables project management inside emails.
  • Vsnap: Allows Vsnap videos to be viewed within emails.

PowerInbox has raised a total of $1.9 million in seed funding from Atlas Venture, Longworth Venture Partners and Correlation Ventures, Egan Managed Capital, Founder Collective, Cloud Capital Partners, Ecosystem Ventures, and a number of angels.

Some users might balk at the idea of re-orienting our web lives back to email in an age where Twitter, Facebook, and others are supplanting many of its uses. But email isn’t going away – even if we sometimes wish it would – so why not make your inbox more efficient?