Support for Microsoft Messenger for Mac ends on April 8th, 2013.
After this date, Messenger for Mac will no longer receive the following:
Software updates from Microsoft AutoUpdate
Messenger users must download the latest version of Skype for Mac and sign in using a Microsoft account. Messenger contacts will be automatically imported to your Skype contact list.
More support lifecycle information
For more information about the Support Lifecycle, visit the Microsoft Support lifecycle web page (http://support.microsoft.com/lifecycle).
To learn more about the support policy, read the Microsoft Support Lifecycle Policy FAQ (http://support.microsoft.com/gp/lifepolicy).