An important abstraction in a messaging system is the message queue (MQ). With a message queue, the sender and the receiver(s) of the message don't necessarily need to be active and connected at the same time to establish a communication, because the queuing system takes care of storing the messages until the destination is able to receive them. This behavior is opposed to the set and forget paradigm, where a subscriber can receive messages only during the time it is connected to the messaging system.
