Apple is notifying OS X Lion users that the platform's preview of Messages will end on December 14th. Originally available as a free beta download for Lion 10.7, Messages went on to become an official feature of Mountain Lion 10.8. Obtained by Cult of Mac, the email from Apple advises that in order to continue using Messages, you'll need to upgrade to Mountain Lion. While it's saddening to have pay for an app that you're accustomed to having for free, keep in mind that this was only a preview. Besides, the upgrade to Mountain Lion is $20 and if you can afford any of Apple's products, we're pretty sure that this expense won't be too much of a stretch. Be sure to take a look at the email in question after the break, because it could be lurking somewhere in your junk mail folder.