Telnet: Test an SMTP server and send an email

In this tutorial, I will explain how to send an email by telneting into an SMTP server.

This manipulation is regularly used to test the correct functioning of an SMTP server.

If you simply want to use Telnet to test a service you can read this tutorial: Using the Telnet client to test a network connection.

We start by connecting to the server:

telnet smtp.domin.com 25

Once connected, we will use the HELO command, indicating the domain that we will use to send a message.

HELO rdr-it.com

The sender of the message is indicated:

MAIL FROM:<telnet@rdr-it.com>

Now we will enter the recipient:

RCPT TO:<romain.******@*******.com>

We enter the DATA command and then enter the body of the message:

DATA

Enter the subject and body of the message and end with . to send the message

Subject: Test message Telnet
Ceci est un message depuis Telnet pour tester un serveur SMTP !
.

The message is sent.

Enter the quit command to log out.

Here is what it looks like in pictures: