Back in October, we announced that the Release to Manufacturing (RTM) build of Exchange Server 2013 was signed off. Since that time, we’ve been focusing our efforts on releasing the next version of Exchange through multiple distribution channels to our business customers.

Today, we’ve reached another important milestone – The Exchange team is excited to announce the general availability of Exchange Server 2013. You can download the bits from TechNet today and evaluate the product for 180 days. You can also sign up for the Office 365 Preview to get the most current Exchange experience in the cloud in just a few minutes.

For those of you who wish to roll out Exchange Server 2013 in greenfield environments, or in labs and test environments to evaluate new features and test with LOB applications, you can start right away. If you are running an Exchange 2010 or 2007 environment, you’ll need Exchange Server 2010 SP3 or 2007 roll up in order to upgrade. We know you are eager to get moving to the new version, so we are hard at work putting the finishing touches on Exchange 2010 SP3 and the roll up, which are on track for release in Q1 of calendar year 2013.

--> Please see the rest on the blog : http://blogs.technet.com/b/exchange/archive/2012/12/03/exchange-server-2013-reaches-general-availability.aspx