A startup called Xobni on Monday released a new, free beta plug-in for Microsoft Outlook that aims to help make e-mail more searchable and more social.

Xobni -- in-box spelled backwards -- appears as a collapsible, vertical sidebar situated on the right-hand side of the Outlook window.

The software's main function is search, and it does that very well.

Xobni indexed the more than 4,500 messages in my in-box in far less time than Windows Desktop Search, and it finds text as I type. Windows Desktop Search for Outlook isn't quite as quick, though it is orders of magnitude faster than searching Outlook without Windows Desktop Search.

"Google went out and organized all the Web's information," said Matt Brezina, co-founder of Xobni. "Yet, there's no Google for personal information. So we just started with the idea that all that information that exists out there, we want to understand and work with better."

Xobni makes Outlook more functional by presenting e-mail as threaded conversations, by organizing attachments, and by extracting and making visible useful information like phone numbers.

"Right now, people have to go and dig through some kind of separate folder that has all their contact information for someone, which I think is totally absurd," said Brezina. "If I'm looking at an e-mail from you and I want to call you, I don't have to have to do any extra work. I just want to see your phone number."

Xobni does this by making e-mail social: It scans through your e-mail to help find connections between e-mail senders and recipients. It thus helps expose latent social networks without requiring users to declare who their friends are or to invite them into a social network.

"The most interesting thing in e-mail is people," said Brezina, who explained that the company arose from the realization that there's an opportunity to structure the information that describes the relationships and the people associated with e-mail.

Brezina co-founded Xobni with Adam Smith in the spring of 2006. Funded by Khosla Ventures, First Round Capital, Y Combinator, Atomico Investments, Baseline Ventures, and a few angel investors, the company plans to make money by offering a premium version of its software to businesses.

Brezina said the premium features have not yet been nailed down. He also said that Xobni was likely to seek revenue from businesses by offering to connect Outlook analytics data and contacts to other popular business communications tools like Saleforce.com.