config error: mail loops back to me?

[phillip.smith at sympatico.ca]

Hi there, hoping this is a common issue with a simple fix...

Someone is trying to use my box for a relay, which sendmail is taking care of nicely, but I keep getting 
A) my inbox filled with messages that for some reason it's trying to deliver locally and B) these strange 
log messages....

> May 24 22:43:37 freedom sm-mta[62410]: h4P2hbFs062410: SYSERR(root):
fre.sg.co.nz.mydomainname.com. config error: mail loops back to me (MX problem?)

If I do an nslookup on this fre.sg.co.nz, i get the following:

Server:  tor-ns1.netcom.ca
Address:  207.181.101.4  <-  my upstream nameserver that I use

Non-authoritative answer:
Name:    fre.sg.co.nz.muydomainname.com
Addresses:  209.82.123.456, 209.167.123.456

Why is my upstream returning this as my domain? I'm not clear on where the issue lies?

If you have an idea, please let me know. Also, if you could CC me it would be great, as I'm not currently 
subscribed to the list.

Many thanks in advance,

phillip.