Not all e-mail is created equal. Some messages may be relevant for years, while others lose meaning within minutes. Yet e-mail in-boxes treat all messages alike, regardless of who wrote them, what they're about, or when they were sent. Adam Smith has set out to change that with Xobni, software that pulls useful information out of e-mails and contextualizes it according to sender.

Smith's goal is to help people unlock and harness the social relationships embodied in their in-boxes. The first version of Xobni (inbox spelled backwards) is a plug-in for Microsoft Outlook and works only on Windows computers--but the results are remarkable.

Once it's installed, Xobni scans every e-mail and extracts information such as a sender's phone numbers, what time she is most likely to e-mail you, who else she has corresponded with, and what files the two of you have exchanged. It labels all the data with descriptive tags, which it then indexes and analyzes. When you click on a specific e-mail, it displays all the information relevant to that sender in a sidebar that runs down the right side of the Outlook window. The tags also allow Xobni to search all indexed e-mails very rapidly.

Smith and his friend Matt Brezina founded Xobni in San Francisco two years ago and have raised $4.25 million from companies including First Round Capital and Khosla Ventures. The plug-in has received one startling endorsement: Bill Gates used it in a public demo at a Microsoft conference, even though the free download remains in beta. There have been rumors of Microsoft's offering around $20 million for Xobni, but the young cofounders didn't bite. Instead, they intend to offer a "Pro" version and à la carte features for sale. Xobni also plans to extend its reach to other e-mail programs, including Web-based services such as Yahoo Mail and Gmail. And the team has already begun building in access to social networks such as LinkedIn.

Other companies have tried to streamline e-mail before. But if Xobni can reach a significant fraction of the world's 400 million Outlook users, Smith may save people time and annoyance by making e-mail more useful. --Om Malik