Use telnet in order to log in on the server SMTP port 25. Below, an example of the interaction between user and server is shown.
> telnet mail.efd.lth.se 25
220 kobra.efd.lth.se ESMTP Sendmail 8.8.8/8.8.8; Thu, 2 Apr 1998 13:17:03 +0200 (MET
DST) HELO datornamn
250 kobra.efd.lth.se Hello marvin.dit.lth.se [130.235.17.74], pleased to meet you MAIL
FROM:<bill@whitehouse.gov>
250 <bill@whitehouse.gov>... Sender ok
RCPT TO:<monica@hotmail.com>
250 <monica@hotmail.com>... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
Howdy!
The main man is on the line, what's cooking?
.
250 SAA28242 Message accepted for delivery
QUIT
>
The user monica will receive a message which looks as if it was sent from a guy living in a large white house.