Simple Mail Transfer Protocol definition messaging
(SMTP) A protocol
defined in STD
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 mhs-relay.ac.uk 25
You should normally start by identifying the local host
You can then issue commands to verify an address or expand an alias:
VRFY firstname.lastname@example.org VRFY postmaster
or expand a mailing list
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.