dynamic dns and e-mail

I am unable to receive outside e-mail. E-smith 4.0 is what I'm using and dnsconsole.com is
the dynamic dns service. If I send myself e-mail, (locally) I receive it whether I use jnash@ xxx.com or
jnash@e-smith.xxx.com in eudora. My web page works fine for outside users, and when I had a friend
trace the e-mail, it says it has been delivered OK. I've tried mail.xxx.com as my MX record and
mail.e-smith.xxx.com, but with no success.
Any help would be appreciated.

Thanks,

Jim Nash

P.S. I think the "e-smith" in the name should be an option during install.