To send an email with telnet from Linux you only need an open terminal and telnet. Then it is simply a matter of opening a connection to your server and sending it some commands. It is the same commands that your GUI mail client will be doing.
Send An Email With Telnet
The following is how to read your emails. When sending emails you need to start the data part with a subject line as show in the box below.
Subject: Your subject
This must be followed by a blank line. The remaining text until the first full stop at the start of a new line will be the message body.
telnet mailserver.dragon.lab smtp
Trying 10.1.200.4…
Connected to mailserver.dragon.lab.
Escape character is ‘^]’.
220 mailserver.dragon.lab ESMTP Postfix
EHLO dragon.lab
250-mailserver.dragon.lab
250-PIPELINING
250-SIZE 4096000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
MAIL FROM: fred@dragon.lab
250 2.1.0 Ok
RCPT TO: fred@dragon.lab
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: Your first test email with POP3
Hello,
This is your first test email.
Fred
.
250 2.0.0 Ok: queued as 57FB240C20
QUIT
221 2.0.0 Bye
Connection closed by foreign host.