You have a little mistake in the "db.mail.geekdept.com" file (misplaced closing parenthesis). It should reads as:

;
;       Addresses and other host information.
;
@       IN      SOA     mail.geekdept.com. hostmaster.mail.geekdept.com. (
                               10118      ; Serial
                               43200      ; Refresh
                               3600       ; Retry
                               3600000    ; Expire
                               2592000    ; Minimum
);       Define the nameservers and the mail servers
               IN      NS      192.168.0.45
               IN      A       192.168.0.45
               IN      MX      10 mail.geekdept.com.