I am not sure if this question has ever been posted or not.  I searched and didn't find anything that seemed to help.
What I have is e-smith 4.1.2 up and working great.  It is connected via a cable modem & using dyndns.org.  That is working great!
My external DNS (for the rest of the internet) is handled by 
www.mydns.com.  MyDNS.com does a great job of re-directing URL's (cloaked and uncloaked), settting up CNAMES, establishing e-mail forwarding etc.  In short I really like it and it hasn't caused me any trouble.
I have my domain parked there and do quite a bit of e-mail forwarding for various people from there.  But what I would like to do is have mydns.com forward MY e-mail to my e-smith machine. (via hostnameX.dyndns.org)  The problem I run in to is that e-smith does returns anything that I forward to it with the message that it does not allow relaying.
What I would like to do is find the easiest/safest way to allow ONE particular host to relay to qmail e-smith box.  (m.dnsix.com)
Anyone have any ideas?
Thanks a ton for any help!!!!