MX record error

I am using the MMC to perfprm DNS on my domain. I am
trying to configure mx records. A select few people can
send email succesfully. the vast majority get a message
kicked back that says,
***********************

The original message was received at Mon, 16 Feb 2004
19:53:56 -0600 (CST)
from cs666863-58.austin.rr.com [66.68.63.58]

----- The following addresses had permanent fatal
errors -----
<fb@dfd.org>
(reason: 550 5.7.1 Unable to relay for URL)

----- Transcript of session follows -----
.... while talking to mail.dfd.org.:
>>> DATA
<<< 550 5.7.1 Unable to relay for URL
550 5.1.1 <fb@dfd.org>... User unknown
<<< 554 5.5.2 No valid recipients


**********************
If I change the mx record to URL the error will
change accordingly.

Can you provide a quick sample, maybe even a screen shot,
of what a good dns, mx record, in MMC not text should look
like.
.

dunno what MMC is, but this is what you've got currently:

Zone Transfer of dfd.org

I don't see any MX records. You need a MX record that looks like this:

dfd.com. MX 10 mail.dfd.com.

And you need an address record like this:

mail.dfd.com. A 66.161.28.175

Then you'd be able to send mail to fb@dfd.org