Sendmail question
 

When I telnet a sendmail SMTP server. How can I use it to send a message?

I know there are easier ways to send a mail...I'm just curious about how it works.

Plenty of webpages about that.

basically

HELO type-some-random-stuff.com
RCPT TO: recipient@domain-that-this-server-is-an-mx-for.com
MAIL FROM: president.shrub@whitehouse.gov
data
Subject: wibble

body of email after a blank line
single period to terminate
.