SMTP and POP3 commands

SMTP and POP3 are the components used to send and receive email. These tables include the actual commands used by email clients.

A great way to verify an email server is to manually execute the SMTP and POP3 commands directly from the command line by typing in the following:

telnet

Outgoing email (SMTP) uses port #25
Incoming email (POP3) uses port #110.

**POP3 Commands (Receive Email)**
Command	Comment
USER	Your user name for this mail server
PASS	Your password.
QUIT	End your session.
STAT	Number and total size of all messages
LIST	Message# and size of message
RETR message#	Retrieve selected message
DELE message#	Delete selected message
NOOP	No-op. Keeps you connection open.
RSET	Reset the mailbox. Undelete deleted messages.

Normal program flow:
USER
PASS
LIST
DELE
QUIT

Accessing your pop3 server manually is useful when a corrupted message is causing your incoming email to abort. This results in the same message being sent over and over. The best way to solve this problem is to telnet into your email server, delete all messages already received and the offending message.

The backspace is not a key to press when running SMTP/POP3 manually. Only one person can access the mailbox at any time.

**SMTP Commands (Send Email)**
Command	Comment
ATRN	Authenticated TURN
AUTH	Authentication
BDAT	Binary data
BURL	Remote content
DATA	The actual email message to be sent This command is terminated with a line that contains only a
EHLO	Extended HELO
ETRN	Extended turn
EXPN	Expand
HELO	Identify yourself to the SMTP server.
HELP	Show available commands
MAIL	Send mail from email account MAIL FROM: me@mydomain.com
NOOP	No-op. Keeps you connection open.
ONEX	One message transaction only
QUIT	End session
RCPT	Send email to recipient RCPT TO: you@yourdomain.com
RSET	Reset
SAML	Send and mail
SEND	Send
SOML	Send or mail
STARTTLS
SUBMITTER	SMTP responsible submitter
TURN	Turn
VERB	Verbose
VRFY	Verify

The following is an actual SMTP session. All sessions must start with HELO and end with QUIT.

HELO my.server.com
MAIL FROM:
RCPT TO:
DATA
From: Danny Dolittle
To: Sarah Smith
Subject: Email sample
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii

This is a test email for you to read.
.
QUIT