Email Relay: In email systems, a relay server forwards messages between senders and recipients. This is commonly used in cases where emails pass through an intermediate server before reaching their destination. However, email relays are also a target for spam if not properly secured.

Network Relay in Communication: In networking, relay stations or routers forward data packets between devices in a network. This is especially useful when direct communication between devices is not possible due to distance, firewalls, or network topologies. Relay in Distributed Systems: In a distributed system, a relay node is a server or intermediary that facilitates the communication between two or more nodes. It helps manage tasks like load balancing, traffic routing, and ensuring that the communication is consistent and reliable. Relay in IoT (Internet of Things): In IoT applications, relay nodes are often used to extend the range of communication between IoT devices and the central server. These relay nodes act as intermediaries to transmit data from edge devices to the cloud.