Why wont this MX record work properly?

[Michael Niksch]

If you are quoting your records literally from your zone file, all names 
are lacking a trailing dot. Within the domain.us zone file,

   arete.domain.us   in  mx  10  mul8.domain.us

will get interpreted as

   arete.domain.us.domain.us.   in  mx  10  mul8.domain.us.domain.us.

and

   mul8.domain.us   in  a  xx.xx.xx.xx

will get interpreted as

   mul8.domain.us.domain.us.   in  a  xx.xx.xx.xx

Most likely, you have indeed omitted the trailing dot after 
mul8.domain.us in the mx record.

-- 
Michael Niksch                     /Zurich/IBM @ IBMCH
IBM Zurich Research Laboratory     nik at zurich.ibm.com
Saeumerstrasse 4                   http://www.zurich.ibm.com/~nik/
CH-8803 Rueschlikon / Switzerland  P: +41-44-724-8913 F: +41-44-724-8080