Gmail

Gmail is a free, advertising-supported webmail, POP3, and IMAP service provided by Google. Gmail was launched as an invitation-only beta release on April 1, 2004 and it became available to the general public on February 7, 2007, though still in beta status at that time. The service was upgraded from beta status on July 7, 2009, along with the rest of the Google Apps suite. As of November 2010, it had 193.3 million users monthly.
With an initial storage capacity offer of 1 GB per user, Gmail significantly increased the webmail standard for free storage from the 2 to 4 MB its competitors such as Hotmail offered at that time. Gmail has a search-oriented interface and a "conversation view" similar to an Internet forum. Software developers know Gmail for its pioneering use of the Ajax programming technique. Gmail runs on Google GFE/2.0 on Linux.