strange DNS problem

[Wojciech Puchar]

one of my users reporting problem sending e-mail to @mil.be

sendmail reports host name lookup failure

host reports

[wojtek at chylonia ~]$ host -t mx mil.be
mil.be mail is handled by 10 hermes01.mil.be.


[wojtek at chylonia ~]$ host -t a hermes01.mil.be
hermes01.mil.be has address 194.7.21.40
hermes01.mil.be has address 193.191.219.40
Host hermes01.mil.be not found: 2(SERVFAIL)
^^^^^^^^^^^^^

where's a problem? while hostr is able to get IP addresses but then 
reports servfail?