Unable to get incoming mails

[Kandhalu Bhaskar]

I have a Linux m/c as a front-end to the internet running BIND 4.9.6.  Then
I have 2 WinNT machines acting as Primary and Seconday DNS servers, again
running on BIND 4.9.6. The secondary DNS machine also acts as Mail server,
running MS Exchange 5.5 + Internet mail service. Recently, the secondary
DNS suffered a disk crash and we had to replace the disk and reinstall NT
server, BIND and MS exchange.

     We had a backup of the db files of BIND and was restored.

     My problem now is that MS exchange is able to send outgoing mails but
incoming mails are getting bounced with the message "The recipient name is
not recognized. Unknown recipient". When I enable the logging in MS
exchange, I can see that the incoming mail is coming as close as upto the
mail server, but then gets bounced from there. I can even see a whole copy
of the incoming mail in the log.

     Is this a problem with the DNS configuration or MS Exchange - Internet
mail service configuration.  And how to resolve this ?

Thanking in advance

Regards

Bhaskar KS