System: Netware 6.5.8 with all current patches.

We are having a problem sending mail to one particular domain ( When a message is sent our GW GWIA returns a "553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)" error message. We receive that error because our mail server is looking at their secondary mx instead of their primary mx. If I unload named then our mail server looks for the secondary external DNS server and mail is sent without error to this domain. When named is not loaded it sends to the correct mx server listed. If I reload named it will work for a while but then default to the incorrect mail server. It also works for a while when I load named -pa, but eventually reverts back to the incorrect server. Could someone help me resolve this issue?