Windows Live Hotmail, formerly known as MSN Hotmail and commonly referred to simply as Hotmail, is a free web-based email service operated by Microsoft as part of its Windows Live group. It was founded by Sabeer Bhatia and Jack Smith and launched in July 1996 as "HoTMaiL". It was one of the first web-based email services. Its original name and capitalization refers to HTML, the encoding language used by the World Wide Web. Hotmail was subsequently acquired by Microsoft in 1997 for an estimated $400 million, and shortly after it was rebranded as "MSN Hotmail". The current version, "Windows Live Hotmail", was officially announced in 2005 and released worldwide in 2007.