SMTP Commands
RFC 821 – Simple Mail Transfer Protocol
Protocol definition for SMTP. This document covers the model, operating procedure, and protocol details for SMTP.
RFC 1869 – SMTP Service Extensions
Definition of the ESMTP extensions for SMTP. This describes a framework for extending SMTP with new commands, supporting dynamic discovery of the commands provided by the server, and defines a few additional commands.
Last updated
| Protocol | Port | Description |
|---|---|---|
| Command | Description | RFC |
|---|---|---|
SMTP
25
SSL/TLS
465
StartTLS
587
HELO
Identifies the sending SMTP server
RFC 5321
EHLO
Extended HELO, provides more information
RFC 5321
MAIL FROM
Specifies the sender’s email address
RFC 5321
RCPT TO
Specifies the recipient’s email address
RFC 5321
DATA
Initiates the message data transmission
RFC 5321
RSET
Resets the session to initial state
RFC 5321
VRFY
Requests verification of an email address
RFC 5321
EXPN
Requests the expansion of a mailing list
RFC 5321
NOOP
No operation, used for testing or keep-alive
RFC 5321
QUIT
Closes the SMTP session
RFC 5321
AUTH
Initiates authentication process
RFC 4954
STARTTLS
Initiates a secure TLS session
RFC 3207
HELP
Requests help information from the server
RFC 5321
