Microsoft may be able to wait for Yahoo, but it's not wasting any time when it comes to buying start-ups. Less than a week after purchasing Farecast for a rumored $115 million, the software giant is back with a new acquisition.

This time it's Xobni, which offers an email sorting plugin and has been lauded by Bill Gates himself. Microsoft has already signed a letter of intent to acquire the company, according to TechCrunch, but terms of the deal have not been announced.

Xobni reportedly turned down a previous offer from Microsoft that was under $20 million.