[CentOS] ssh security

Cisco-Education wrote:
<snip>
> Jun 19 16:26:06 kmdns1 sshd[11073]: Invalid user jeka from 87.118.122.78
> Jun 19 16:26:06 kmdns1 sshd[11074]: input_userauth_request: invalid user jeka
> Jun 19 16:26:06 kmdns1 sshd[11074]: Received disconnect from
> 87.118.122.78: 11: Bye Bye
<snip>
> Now both the Mail server and the backup pc server behind firewall and ssh
> protocol is denied to the hosts in the DMZ zone

doesn't look like it :-)
check your firewall, ssh is definitely getting through to that mail server.