As Microsoft tries to get an edge in free email service, the company is switching all Hotmail users to its new Outlook.com service and spending millions on a massive ad campaign.

Microsoft is so confident it has the Internet's best email service that it’s spending at least $30 million to send its message across the U.S.

   The barrage began Tuesday when Microsoft's twist on email escalated an assault on rival services such as Google’s Gmail.

Outlook email is getting good reviews so far.  Critics said it's a streamlined email experience with tight integration with Facebook and Twitter and Microsoft's cloud service, SkyDrive.

Since the test version was made available last summer, 60 million people have joined Outlook.com.

Hotmail users can go online and manually switch, but Microsoft will move all Hotmail accounts over by summer.

Mail to the Hotmail addresses will be forwarded to the new Outlook.com address.

   To welcome new users, Microsoft is financing what it believes to be the biggest marketing blitz in the history of email.

Outlook.com will be featured in ads running on primetime TV, radio stations, websites, billboards and buses.

Microsoft expects to spend somewhere between $30 million to $90 million on the Outlook campaign, which will run for at least three months.