This is a simple howto for future reference:

This is an easy way to test if a mail server is configured correctly

Simple manual telnet session with mail host
Uppercase/lowercase does not appear to be significant.

Try this

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 Tells you to send data then CRLF period CRLF at end

You type your message then CRLF period CRLF (ie, type a period on a line by itself then hit ENTER)

QUIT Signoff message