Delete for hosts, not reachable by web-frontend

[mbrand5371]

Hi!

Our ZABBIX logfile consists entrys like:

  9521:20121030:094958.807 cannot send list of active checks to [10.100.196.241]: host [CMSCOG11.dmz.dummy.dummy.de] not found
  9521:20121030:095010.935 cannot send list of active checks to [10.100.216.241]: host [smscog11r.dmz.dummy.dummy.de] not found
  9519:20121030:095012.022 cannot send list of active checks to [10.100.216.201]: host [smseps12r.referenz.dummy.dummy.de] not found
  9513:20121030:095047.001 cannot send list of active checks to [10.100.216.200]: host [smseps11r.referenz.dummy.dummy.de] not found
  9515:20121030:095047.006 cannot send list of active checks to [10.100.216.204]: host [smssql11r.referenz.dummy.dummy.de] not found

These Hosts are removed from the network since more than 3 months.
I cannot delete the hosts from the hostgroup.
They are not available in hosts-screen or searchable in web-frontend, using the hostname or hostip.

How can i delete these hosts from the configuration?
Regards, Marcus