I am sorry. You're right. I tried it but with wrong. I corrected it and now it works.
But I had to change this:
$rcmail_config['password_query'] = 'SELECT update_passwd(%c, %u)';
to:
$rcmail_config['password_query'] = "UPDATE vmail.mailbox SET password=%c,passwordlastchange=NOW() WHERE username=%u LIMIT 1";
Is it OK?
error message was:
[Fri May 03 08:30:07 2013] [error] [client x.x.x.x] PHP Warning: Error writing to log file /srv/www/roundcubemail-0.9.0/logs/errors; Please check permissions in /srv/www/roundcubemail-0.9.0/program/lib/Roundcube/rcube.php on line 1056, referer: https://mail.domain.com/mail/?_task=set … n.password
[Fri May 03 08:30:07 2013] [error] [client x.x.x.x] PHP Notice: [1305] FUNCTION vmail.update_passwd does not exist in /srv/www/roundcubemail-0.9.0/program/lib/Roundcube/rcube.php on line 1140, referer: https://mail.domain.com/mail/?_task=set … n.password
client x.x.x.x - my ip address
mail.domain.com - the system hostname