Two issues I can see :-
1) DNS ERROR - none of the MX records for nirmal123.no-ip.biz Fri Jul 11 14:10:16 2008 resolve to this host
2) Fri Jul 11 14:18:45 2008 Port conflict detected: 25 (zimbra-mta)
So the second one looks like you have either SendMail or Postfix already running on that server, so please remove them or shutdown the service.
For the other one it looks like your DNS is wrong. Please post
Code:
cat /etc/hosts
cat /etc/resolv.conf
dig _yourdomain_ mx
dig _yourserverfqdn_ a
host `hostname` <- note backticks and not double quotes