Microsoft has acquired Xobni, likely for more than its original $20 million offer to buy the company, TechCrunch's Michael Arrington reports. Xobni — "inbox" spelled backward — adds features to Outlook, Microsoft's desktop email application. As VC blogger Fred Wilson notes, the acquisition is "sort of proof that Microsoft doesn't know how to improve its own software. So they buy those that do." If Arrington's report proves more accurate than previous rumors of a sale, Xobni CEO Jeff Bonforte would join Microsoft well before his former colleagues at Yahoo, where Bonforte worked just long enough to be paid to leave.