Thanks to Jeff - The EXPTA {blog}, you can have full how-to " use telnet to send SMTP email" for some basic testing and such.
I’ve ran into A lot of issues when migrating to Exchange 2007 / Exchange 2010 , due to the strict RFC compliance that Microsoft has implemented with the new transport (SMTP) stack.
anyways, enjoy this fine how-to:
http://www.expta.com/2010/03/how-to-use-telnet-to-send-smtp-email-to.html