Post Office Protocol 3 (POP3): POP3 is one of the three email protocols. It is most commonly used by email clients to allow email to be received. This protocol uses Transmission Control Protocol: TCP divides data into data packets that can be sent safely and quickly while minimizing the chance of data loss. It offers a stable and reliable mechanism for the transmission of data packets in an IP-based network. Although TCP is an effective, connection-oriented protocol, it adds overhead. for the administration and delivery of an e-mail.