SMTP stands for Simple Mail Transfer Protocol, which is a widely used communication protocol for electronic mail transmission. Although there are no exact synonyms for SMTP, there are some related terms that can be used to describe it. For instance, email servers are also known as mail transfer agents or message transfer agents. Moreover, email clients such as Outlook or Gmail use various protocols to send and receive email messages, including SMTP, POP3, and IMAP4. Another related term is MTA (Mail Transfer Agent), which is a software application that routes electronic messages across the Internet. However, SMTP remains the most commonly used term to refer to the protocol used for email transmission.