Problem with qmail

[jagrok]

Hello i have a problem with qmail , when i try to change a maximum of latter in the plesk in the server -> mail i get this messege :

Unable to set up maximum letter size: mailmng failed: mailmng: Unable to open file databytes: Permission denied System error 13: Permission denied

0: /opt/psa/admin/plib/common_func.php3:169
psaerror(string 'Unable to set up maximum letter size: mailmng failed: mailmng: Unable to open file databytes: Permission denied System error 13: Permission denied')
1: /opt/psa/admin/htdocs/server/mail.php3:76

Did you know mabe what i must do it ?
and what file must be a permission and what gruop and users i must used ?

 

[Cranky]

rm -f /var/qmail/control/databytes
echo '0' > /var/qmail/control/databytes
chmod 644 /var/qmail/control/databytes

This should then allow you to change it.