Overview
Message Queuing (also known as MSMQ) is a server application that enables applications to communicate across heterogeneous networks and systems that may be temporarily offline or otherwise inaccessible. Instead of an application communicating with a service on another computer, it sends its information to Message Queuing, which sends the information to a Message Queuing service on the target computer where it is made available to the other application. Message Queuing provides guaranteed delivery, efficient routing, security, and priority based messaging.
http://www.microsoft.com/en-us/download/details.aspx?id=36775