Microsoft Messenger service
Messenger (formerly MSN Messenger Service, .NET Messenger Service and Windows Live Messenger Service) is an instant messaging and presence system developed by Microsoft in 1999 for use with its MSN Messenger software and used today by its instant messaging clients including Windows 8, Windows Live Messenger, Microsoft Messenger for Mac, Outlook.com and Xbox Live. Third-party clients also connect to the service. It communicates using the Microsoft Notification Protocol, a proprietary instant messaging protocol. The service allows anyone with a Microsoft account to sign in and communicate in real time with other people who are signed in as well. In early 2013, Microsoft is ending its Messenger service and is encouraging users to merge their Messenger accounts into new or existing Skype accounts.
Despite multiple name changes to the service and its client software over the years, the Messenger service is often referred to colloquially as "MSN", due to the history of MSN Messenger. The service itself was known as MSN Messenger Service from 1999 to 2001, at which time, Microsoft changed its name to .NET Messenger Service and began offering clients that no longer carried the "MSN" name, such as the Windows Messenger client included with Windows XP, which was originally intended to be a streamlined version of MSN Messenger, free of advertisements and integrated into Windows.
Nevertheless, the company continued to offer more upgrades to MSN Messenger until the end of 2005, when all previous versions of MSN Messenger and Windows Messenger were superseded by a new program, Windows Live Messenger, as part of Microsoft's launch of its Windows Live online services.
For several years, the official name for the service remained .NET Messenger Service, as indicated on its official network status web page, though Microsoft rarely used the name to promote the service. Because the main client used to access the service became known as Windows Live Messenger, Microsoft started referring to the entire service as the Windows Live Messenger Service in its support documentation in the mid-2000s.
The service can integrate with the Windows operating system, automatically and simultaneously signing into the network as the user logs into their Windows account. Organizations can also integrate their Microsoft Office Communications Server and Active Directory with the service. In December 2011, Microsoft released an XMPP interface to the Messenger service.
Official clients 
Microsoft offers the following instant messaging clients that connect to the Messenger service:
- Windows 8, includes a built-in Messaging client
- Windows Live Messenger, for users of Windows 7 and previous versions
- Microsoft Messenger for Mac, for users of Mac OS X
- Outlook.com includes web browser-based functionality for instant messaging
- Xbox Live includes access to the Messenger service from within the Xbox Dashboard
- Messenger on Windows Phone includes access to the Messenger service from within a phone running Windows Phone
- Windows Live Messenger for iPhone and iPod Touch includes access to the Messenger service from within an iPhone, iPod Touch or iPad
- Messenger Play! includes access to the Messenger service from within an Android phone or tablet
- Windows Live Messenger for Nokia includes access to the Messenger service from within a Nokia phone
- Windows Live Messenger for BlackBerry includes access to the Messenger service from within a BlackBerry
Third-party clients 
|This section does not cite any references or sources. (November 2009)|
Additionally, these third-party clients and others can access the Messenger service:
- Adium (Mac OS X, GPL)
- aMSN (multi-platform, GPL)
- Ayttm (multi-platform, GPL)
- BitlBee (Windows and Unix-like, GPL)
- CenterIM (cross-platform, GPL)
- emesene (multi-platform, GPL)
- Empathy (Linux GNOME, GPL)
- eBuddy (Web-based and mobile)
- Fire (Mac OS X, GPL)
- XMPP (any client supporting XMPP protocol can use transports to connect to the Messenger service)
- KMess (Linux KDE, GPL)
- Kopete (Linux KDE, GPL)
- Meebo (Web-based)
- Meetro (multi-platform, proprietary)
- Miranda IM (Windows, GPL)
- Pidgin (formerly Gaim) (multi-platform, GPL)
- PlayXpert (Windows, proprietary)
- tmsnc (multi-platform, text based)
- Trillian (multi-platform, Web, proprietary)
- Yahoo! Messenger (multi-platform, proprietary)
Windows NT Messenger Service 
Windows NT and newer operating systems from Microsoft included a system notification service called Messenger service, which was intended for use within workgroups, but eventually became used maliciously to present pop-up advertisements to users. This service, although it has a similar name, is not related in any way to the Microsoft Messenger Service or the Windows Messenger instant messaging client. It became disabled by default with Windows XP Service Pack 2 and Windows Server 2003 Service Pack 1 and was removed completely in Windows Vista and Windows Server 2008.
Microsoft Messenger has been criticized for the use of the Microsoft Notification Protocol, which does not provide any encryption. This makes wiretapping personal conversations in Messenger a trivial task if someone intercepts the communication, which is easy in an unencrypted public Wi-Fi networks.
Microsoft announced on April 8, 2013, that the service would be merged and replaced by Skype, which had been recently purchased by Microsoft beforehand. The staff reported that all Messenger services would be shutdown in every country the service was running in, in exclusion to China, in the first quarter of next year.
See also 
- Microsoft Notification Protocol
- Comparison of instant messaging protocols
- Comparison of instant messaging clients
- Microsoft Launches MSN Messenger Service
- Microsoft Help and Support: Important changes to Windows Live Messenger
- Get Started with Windows Messenger v4.0
- Check the Microsoft .NET Messenger Service status
- Messenger service status
- Get Messenger on your smartphone—it’s easy and it’s free! Retrieved 7 September 2012