perl: warning: Setting locale failed.

[prale]

hello, after I installed, munin, amavis and maia my email get's bombed every 5mins:

FROM: Cron DEAMON

Cron <munin@domain> if [ -x /usr/bin/munin-cron ]; then /usr/bin/munin-cron; fi

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "de_DE.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "de_DE.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "de_DE.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "de_DE.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

----------------------------------------------------------

Also I get the same one but then from amavis.

What can I do?
I beleive I have only installed nl_NL.utf8
I don't know how to install de_DE.UTF8, or change the setting to nl_NL.utf8.

Please help me, I get already more than 200emails a day :S