In 2000, individual corporate users sent and received about 15 e-mails a day. Today, about 133 messages are zipping back and forth.

Yet despite the explosion of e-mail, the most popular corporate e-mail program, Microsoft Outlook, hasn't changed much. The more you use it the slower it gets; it's hard to search through messages to find a phone number or attachment.

This week a company called Xobni ("inbox" spelled backward, pronounced "zob-nee") released a free downloadable program to help you control your Inbox at Xobni.com. Once installed, Xobni runs inside of Outlook and indexes and analyzes all of your messages to give you information about each person with whom you've exchanged e-mails.

When you highlight a message in your inbox, Xobni displays the sender's profile in a sidebar beside your inbox. Each profile is like a thick file on every person you e-mail. The more you communicate with them, the bigger the file.

Don't have someone's a phone number? Xobni scours your address book, e-mail signatures at the bottom of messages and the text of e-mail messages to display your contact's phone number in his profile, even if he isn't in your address book.

Not sure when is the best time to send someone an e-mail? Each profile contains a graph showing the times of day they e-mail you the most.

Need to reach someone's assistant but can't remember the name? Each Xobni profile lists people who are often copied on messages to you.

Xobni's other main feature is its search function, which is contained in the sidebar.

But it could be a lot more useful. It would be nice if Xobni could, for example, let you know when you haven't responded to a top contact in a few days.

And once you permanently delete a message, Xobni loses track of it.