Outlook.com, formerly known as Hotmail, has been the top email provider in the U.S.. Google’s updated numbers show that they now take the place of Outlook.com, as the most used email service.

Gmail reported that they had 425 million users in 2012, now up to 900 million in 2015. 75% of the 900 million active users access their Gmail login from mobile devices, giving an indication of the attention that Google has given to making Gmail user friendly on mobile devices.

Google continues to develop apps and services such as Google Play, Youtube, Picasa, Maps, Google Drive and Chrome that will bring more users into the Gmail fold, as these services are discovered.

Sources:
http://www.google.com/about/products/
http://emailhelpr.com/gmail-login/
http://techcrunch.com/2015/05/28/gmail-now-has-900m-active-users-75-on-mobile/