Question on rule

I have a question to creating a rule:

CREATE RULE dbmail_mailboxes_autocreate AS ON INSERT TO dbmail_users DO
ALSO insert into dbmail_mailboxes (owner_idnr,name) values
(NEW.user_idnr,'INBOX'), (NEW.user_idnr,'Gesendete Objekte'),
(NEW.user_idnr,'Entwürfe'), (NEW.user_idnr,'Junk'),
(NEW.user_idnr,'Papierkorb');
ERROR: VALUES must not contain OLD or NEW references
TIP: Use SELECT ... UNION ALL ... instead.

But in http://www.postgresql.org/docs/8.3/interactive/rules-update.html
the examples also use NEW in the values. Or can I only use a rule within
the same table?

If I need to use a TRIGGER: I tried with creating a function, but I
don't know how to pass the current user_idnr to that function from the
trigger. I managed to create the function:

CREATE FUNCTION dbmail_mailboxes_autocreate_function(user_idnr bigint)
returns integer AS $$ BEGIN insert into dbmail_mailboxes
(owner_idnr,name) values (user_idnr,'INBOX'), (user_idnr,'Gesendete
Objekte'), (user_idnr,'Entwürfe'), (user_idnr,'Junk'),
(user_idnr,'Papierkorb'); END; $$ LANGUAGE plpgSQL;

But I don't know how to do the trigger. Can someone help me?

mfg zmi
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