An interprocess communication (IPC) mechanism in Microsoft Windows operating systems that provides connectionless, datagram-based one-to-one or one-to-many communication between processes on different computers. Mailslots are similar to named pipes, which also provide communication between two processes. However, the communication through a named pipe is one-to-one and two-way, while the communication through a mailslot can be one-to-many and is only one-way.
Mailslots are implemented as file system drivers, and therefore:
Mailslots were originally developed for Microsoft OS/2 LAN Manager and have been maintained in Windows for backward compatibility. They are usually used for broadcast purposes, such as service announcements.
Mailslots are used in the Computer Browser service on Windows NT and in the WinPopUp messaging tool in Windows 95 and Windows 98, among other places.