[imp] Qmail problem in changing password with Horde

[Gmail]

I setup horde to work with qmail, vpopmail (mysql enable). When I change password through horde’s account panel, value in clear text password (pw_clear_passwd) is changed but encrypted password (pw_passwd) is not.
So,how to config horde to change encrypted password along with clear text password?
 
Here my info:
OS: Fedora core 6
Mail: Qmailtoaster, vpopmail with mysql, horde webmail.