SMTP

This term is a technical acronym used exclusively within the domain of computer networking and email infrastructure. It describes the specific set of rules that govern how mail servers communicate to route messages from a sender to a recipient.

As a technical specification, it is treated as a singular entity. In professional documentation, it is often paired with related protocols like POP3 or IMAP to describe a complete mail system. It is rarely used in casual conversation unless the speaker is discussing technical configuration or troubleshooting email delivery issues.