In what some see as a clear admission of defeat in the mobile email market, troubled cell phone maker Motorola on Tuesday said it is selling an email company it acquired two years ago for an undisclosed sum.

The unit is being sold to Redwood City, California-based Visto, a venture-backed company that sells mobile email products and services to carriers such as Rogers Wireless, Vodafone, and Sprint Nextel. (Visto Gets $35M Mail Call)

Motorola paid a reported $450 million for Good Technology, the acquisition that became its mobile messaging unit, in late 2006.

Back then BlackBerry maker Research In Motion was in the process of getting a firm grip on the market, and both Motorola and Nokia were licensing Good Technology’s products.

“Back then there was easy access to cheap credit and Motorola was flying pretty high with its RAZR so everything was nicely aligned, so it was an easy decision to make,” said David Chamberlain, principal analyst at In-Stat.

But times have changed.

Motorola has since suffered a series of financial setbacks and is now getting rid of Good Technology for what most assume is far less than it paid for it. (Motorola Reports Loss on Mobile Weakness)

“With this deal, Motorola officially declares defeat in the enterprise cell phone battle to other players like RIM,” said Shahid Khan, senior partner with IBB Consulting.  “This deal allows them to unload a failed business. In my opinion, they should just get rid of their entire cell-phone unit.”

Blaming “stresses in the financial markets” Motorola late last year delayed an expected split of the company that would’ve separated the foundering cell phone unit from the rest of the company.

Motorola, which remains a handset leader in the U.S. market, is likely to divert its mobile applications focus away from business apps and toward consumer offerings such as social networking. (Motorola Betting it All on Google)

“But they face a tough competition from Apple, Nokia, and Samsung in this space, as well,” Mr. Khan said.

For  Visto, this is a deal that makes sense. The company has spent about $150 million building and marketing a mobile messaging system designed for carriers.

Now the 12-year-old company, which has filed a series of lawsuits against a number of rivals, gets to mesh the Good unit, which is aimed at enterprises, with its existing carrier-focused business.

Visto,  backed by DFJ Growth Fund and Blueprint Ventures among others, has filed patent infringement suits against Microsoft, RIM, Good Technology, and Seven Networks.

In December 2007, Visto was awarded $7.7 million in a patent infringement suit against mobile email firm Seven. Visto reached a financial settlement with Microsoft in March 2008.