Microsoft Messenger for Mac

Microsoft Messenger for Mac (previously MSN Messenger for Mac) is the official Mac OS X instant messaging client for use with Microsoft's .NET Messenger Service and is developed by the Macintosh Business Unit, a division of Microsoft. However, the feature list is limited in comparison to that of its counterpart Windows Live Messenger. The client is still maintained and updated but still lacks a number of features that its Windows counterpart contains. In response[citation needed] to its lack of features third-party competitors have been developed, such as Adium and aMSN

Resource: Wikipedia