In the context of electronic mail, the term indicates that a message is awaiting transmission. It is held temporarily in a system, typically a mail server, before being sent to its intended recipient. For example, if a mail server is experiencing high traffic or is temporarily unavailable, outgoing messages will be placed in a holding area until the server can process and deliver them.
The act of holding messages for later delivery is crucial for ensuring reliable communication. It provides a buffer against temporary network issues or server overloads, preventing messages from being lost. Historically, this functionality has been essential in environments with unreliable network connectivity, guaranteeing eventual delivery despite intermittent disruptions.