SMTP
Simple Mail Transfer Protocol
Application Layer — Email
Protocol Overview
Full Name
Simple Mail Transfer Protocol
Abbreviation
SMTP
OSI Layer
Application Layer
Category
Email
Default Port
25, 465, 587
RFC
RFC 5321
About SMTP
Standard protocol for sending email between mail servers. Handles message routing, delivery, and relay across the internet.
Application Layer
Email
Port 25, 465, 587
Standards Reference
SMTP is defined in RFC 5321, published by the Internet Engineering Task Force (IETF). RFCs are the official standards documents for internet protocols and are freely available for public review.