(Telecompaper) Microsoft's Outlook.com has attracted 60 million active users in the first six months, a third of them having switched from Google's Gmail, according to Microsoft. The software giant said Outlook.com was the world's fastest growing e-mail service. Microsoft is launching the service formally after a six-month "preview period". From 18 February, Microsoft will start upgrading every Hotmail user to Outlook.com seamlessly. They will keep their @hotmail.com address, user ID, password, contacts, etc.