Simple Mail Transfer Protocol

(redirected from Port 587)

Simple Mail Transfer Protocol

[¦sim·pəl ′māl ‚tranz·fər ‚prōd·ə‚kȯl]
(computer science)
An Internet standard for sending e-mail messages. Abbreviated SMTP.

Simple Mail Transfer Protocol

(SMTP) A protocol defined in STD 10, RFC 821, used to transfer electronic mail between computers, usually over Ethernet. It is a server to server protocol, so other protocols are used to access the messages. The SMTP dialog usually happens in the background under the control of the message transfer agent, e.g. sendmail but it is possible to interact with an SMTP server using telnet to connect to the normal SMTP port, 25. E.g.

telnet 25

You should normally start by identifying the local host:


You can then issue commands to verify an address or expand an alias:

VRFY VRFY postmaster

or expand a mailing list:

EXPN c-help

You can even send a message:

MAIL From:<> RCPT To:<> DATA What is the point? . QUIT

This is useful if you want to find out exactly what is happening to your message at a certain point.

See also Post Office Protocol, RFC 822, sendmail.
References in periodicals archive ?
In one example reported by Spamhaus, a major ISP, allegedly home to 25 percent of e-mail seam that originated inside the United States, moved its Web-based email traffic from Port 25, which does not require authentication, to Port 587, which requires an account ID and password to send e-mail.
While moving to Port 587 will not stop a zombie from sending spam, it will require that zombie to identify itself to the system, which helps in tracking and cleanup.