tux-mobile:/home/tuxito# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 server1.example.com ESMTP Postfix (Debian/GNU)
MAIL FROM: tuxito@server1.example.com
250 2.1.0 Ok
RCPT TO: tuxito@server1.example.com
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: Campo de Prueba
From: tuxito@server1.example.com

Hola,
esto es una prueba.
Adios.
.
250 2.0.0 Ok: queued as DD68CD593
quit
221 2.0.0 Bye
Connection closed by foreign host.
tux-mobile:/home/tuxito#