DNS problem

[Kandhalu Bhaskar]

Hi all,

     We have a Linux 4.2 machine as firewall and running BIND 4.9.6. Apart
from that, we have 2 Windows NT machines as Primary and Secondary DNS
servers. The secondary also acts as mail server running MS Exchange 5.5 /
Internet mail servcice.

     Of late, we are having problems receiving mail from the internet,
while we are able to send outbound mails. The following error message
appears in the bounced mail.

"The specified address contains a host or domain name that could not be
found by the Domain Name Server or local hosts file."

     Can you help me out in identifying the bug and how to fix it ?

Thanking in Advance

Cheers

Bhaskar