SMTP server - send email via telnet

To send e-mail via telnet (and test the smtp server setup):

telnet smtp.example.com 25 

helo smtp.example.com
mail from:<user@example.com>
rcpt to:<user2@customer.com>
data
From: test@mydomain.com
Subject: test mail from command line

this is test number 1
sent from linux box
.
quit

For starttls:

 ehlo smtp.example.com