Hi,

the SMTP protocol is ASCII based. In the past, the SMTP protocol goes unencrypted over the wire means you can simply send emails by connecting to the SMTP port 25 and enter some SMTP commands via telnet:

michael@debdev ~ # telnet smtp.yourdomain.org 25
EHLO test.example.com
MAIL FROM:info@yourdomain.org
RCPT TO:receiver@receiversdomain.org
DATA
Subject: Testmessage
<ENTER>
<ENTER>
This is a test message. End with <ENTER><ENTER> and point

.
QUIT

Continue reading Mail: Connect TLS encrypted to a smtp server by telnet →