Send Email via Telnet

Telnet to hostname on port 25
HELO your_domain_name or whatever
MAIL FROM:you@hostname.com (ie, your email address)
RCPT TO:them@someplace_else.com (email address you want to send to)
DATA
You type your message then CRLF period CRLF (ie, type a period on a line by itself then hit ENTER)
QUIT