The SMTP (Simple Mail Transfer Protocol) is an Internet standard for electronic mail (Email) transmission across Internet Protocol (IP) networks.
This tutorial shows how to connect to SMTP mail server and send an Email using the ‘telnet’ command.
Step 1: Open a connection from your computer to an SMTP mail server
$ telnet smtp.domain.ext 25 220 smtp.domain.ext ESMTP Sendmail ?version-number?; ?date+time+gmtoffset?
- smtp.domain.ext – Your mail server;
- 25 – Default port for SMTP.
Step 2: Declare your domain name or IP-address
You can set local.domain.name or anything you want in ‘HELO’, because the server doesn’t check its authenticity, that is one of the drawbacks of this protocol.
> HELO local.domain.name 250 smtp.domain.ext Hello local.domain.name [xxx.xxx.xxx.xxx], pleased to meet you
Step 3: Set sender’s email
> MAIL FROM: email@example.com 250 2.1.0 firstname.lastname@example.org... Sender ok
Step 4: Set recipient’s email
> RCPT TO: email@example.com 250 2.1.5 firstname.lastname@example.org... Recipient ok
Step 5: To write the message, type DATA and press ‘Enter’
> DATA 354 Enter mail, end with "." on a line by itself
Step 6: On the first line type ‘SUBJECT: Your Subject’ and press ‘Enter’ twice
> SUBJECT: Test message
Step 7: Continue typing your message
Hello, this is a TEST message, please don't reply. Thank you.
Step 8: Put a single period (.) on a line by itself and press ‘Enter’ to send your message.
> . 250 2.0.0 ???????? Message accepted for delivery
Step 9: Close the connection
> QUIT 221 2.0.0 server.com closing connection