Windows Messenger service

Messenger service was a network-based system notification Windows service by Microsoft that was included in some earlier versions of Microsoft Windows. This retired technology, although it has a similar name, is not related in any way to the later, Internet-based Microsoft Messenger service for instant messaging or to Windows Messenger and Windows Live Messenger (formerly named MSN Messenger) client software.

Source: Wikipedia — Windows Messenger service (CC BY-SA 4.0)