This morning Yahoo officially relaunched Yahoo Mail, ending a two-year public test of the Web-based email service that began in September 2005. Its overhaul completed, Yahoo Mail is no longer just a Webmail client, it’s a “social communication” tool. “Our goal is to make (Yahoo) Mail a more social experience,” John Kremer, vice president of Yahoo Mail, told Reuters. “We really look at ourselves as sitting on top of the largest dormant social network out there.”

To that end, Yahoo Mail now boasts SMS (short message service) support, offering its users the ability to send text messages to cellphones. It’s the first free Web-based email service to offer that feature, and it’s almost certainly starting a trend by doing so. Notes Paul Ruppert, founder of mobile-market consultancy Global Point View, SMS usage is exploding: “The future of mobile messaging with over 3 trillion text messages annually would logically seem well secured,” he wrote in a post to Mobile Messaging 2.0. “A well of demand currently from 2.1 billlion users globally is not going to dry up over night. Plus, all the trends are upward. There is revenue and SMS usage growth in even the most mature country markets such as the U.K. Message-dense nations with high percentages of young populations, mostly in Asia, continue to come online to mobile. Even in markets like the U.S., which lagged in embracing the ease and power of texting and seemingly preferred email and instant messaging, text messaging has become an intimate aspect of daily lives, especially for those 15 to 25.”