SMTPSimple Mail Transfer Protocol (SMTP) is the standard protocol for sending emails across the Internet. Therefore, SMTP transfers messages from the senders mail servers to the recipients mail server.Additional InformationTCP:TCP is the transfer layer protocol. Electronic mail function is supported by the transfer layer protocol TCP. TCP is a connection-oriented and reliable transport protocol. Therefore, SMTP transfer messages from the senders mail servers to the recipients mail servers using TCPUDP:UDP is an unreliable connectionless-transport layer Protocol used for its simplicity and efficiency in applications where error can be provided by the application layerUDP provided process-to-process communication