how to send yourself an email from George@Whitehouse.com
your email is: username@domain.suffix

first open a telnet session:
c:\windows>telnet domain.suffix 25

(the lines with the numbers are the server responses)
===================================
220 ....
helo
250 HELO ...
mail from:<George@Whitehouse.com>
250 Ok
rcpt to: username@domain.suffix
250 Ok
data
354 end your data with .
This is a test message.
.
250 Ok
quit
221 BYE
===================================