Before email program like Outlook or Mozilla thunderbird exists, telnet is the program you use to send email. This method is considered old enough and it exist at the beginning of the internet itself.
The items in bold are what you should type.
Start telnet by the following command at your command prompt/shell
telnet inertz.org 25
220-my.internet-webhosting.com ESMTP Exim 4.68 #1 Sun, 24 Feb 2008 11:17:08 +080
0
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
helo
250 my.internet-webhosting.com Hello [124.13.133.112]
mail from: [email protected]
250 OK
rcpt to:[email protected]
250 Accepted
data
354 Enter message, ending with “.” on a line by itself
This is test.
.
250 OK id=1JT7R9-00066M-7Z
quit
221 my.internet-webhosting.com closing connection
Connection to host lost.