Yes, that message display when I try to start apache inside my jail box.
 [Thu Jul 10 13:23:41 2008] [alert] mod_unique_id: unable to gethostbyname(â€mailserverâ€)
To resolve this problem, just edit /etc/hosts
add record for ‘mailserver’ entry, like :
::1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â localhost localhost.my.domain
127.0.0.1Â Â Â Â Â Â Â Â Â Â Â Â Â Â localhost localhost.my.domain
172.88.1.5Â Â Â Â Â Â Â Â Â Â Â Â Â email.rasyid.com mailserver
Restart apache and test it yourself.