I have setup successfully iredmail 0.5.0-beta 3 on debian lenny 5.0.1 .
After i make everithing work  by editing  /etc/dovecot/dovecot-mysql.conf
------------------------------------/etc/dovecot/dovecot-mysql.conf------------------------------------------------------
driver = mysql
default_pass_scheme = CRYPT
connect = host=localhost dbname=vmail user=vmail password=LQ5rVbCsyc1DcghofkSGXds2wQKI9f

password_query = SELECT password FROM mailbox WHERE username='%u' AND active='1' AND expired >= NOW()
user_query = SELECT CONCAT("/home/vmail/", maildir) AS home, 1001 AS uid, 1001 AS gid, CONCAT('*:bytes=', quota*1048576) AS quota_rule FROM mailbox WHERE username='%u' AND active='1' AND enable%Ls='1' AND expired >= NOW()
----------------------------------------------------------------------------------------------------------------------------------------
and
--------------------------------/etc/dovecot/dovecot.conf------------------------------------------------------------------------
#mail_uid = 1001
#mail_gid = 1001
first_valid_uid = 1001
last_valid_uid = 1001
----------------------------------------------------------------------------------------------------------------------------------------
note : uid and gid is the uid and gid of the user vmail ! without this modificatio do not work on my debian .
Now everything is working .

And here is  the question :

HOW CAN I SETUP VACATION AND OUT OFF OFFICE MESSAGES ON IREDMAIL ?

Thank you very much .