[Dovecot] Help with implementing quota warning

[Joy]

Dear All,
               I am using the latest version of doveot-2.0.6 and using
dovecot-lda to deliver mail in to Maildir. I have successfully
implemented the global quota as well as per user quota using ldap for
storing per user quota. Now i am trying to send warning message when
user exceed quota limit of 80% and 95% but unable to implement the
same.

Here is the output of doveconf -n

# 2.0.6: /usr/local/dovecot/etc/dovecot/dovecot.conf
# OS: Linux 2.6.35-22-generic i686 Ubuntu 10.10
base_dir = /var/run/dovecot/
disable_plaintext_auth = no
hostname = mail.example.net
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
listen = *
log_path = /var/log/imap
login_greeting = IMAP4 and POP3 server ready to serve you.
mail_location = maildir:~/Maildir
mail_plugins = " acl quota"
passdb {
  args = /usr/local/etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
plugin {
  acl = vfile:/usr/local/dovecot-acl/acl:cache_secs=3600
  autocreate = Sent Items
  autocreate2 = Drafts
  autocreate3 = Spam
  autocreate4 = Deleted Items
  autosubscribe = Sent Items
  autosubscribe2 = Drafts
  autosubscribe3 = Spam
  autosubscribe4 = Deleted Items
  quota = maildir:User quota
  quota_rule = *:storage=1G
  quota_warning = storage=95%% /usr/local/bin/quota-warning.sh 95 %u
  quota_warning2 = storage=80%% /usr/local/bin/quota-warning.sh 80 %u
}
postmaster_address = admin at example.net
protocols = imap pop3
service imap-login {
  inet_listener imap {
    port = 143
  }
}
service pop3-login {
  inet_listener pop3 {
    port = 110
  }
}
service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  unix_listener quota-warning {
    user = vmail
  }
  user = dovecot
}
ssl = no
userdb {
  args = /usr/local/etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol lda {
  mail_plugins = " acl quota"
}
protocol imap {
  mail_plugins = " acl quota autocreate imap_acl imap_quota"
}
protocol pop3 {
  mail_plugins = " acl quota"
}


Here is quota-warning.sh content

#!/bin/sh
PERCENT=$1
USER=$2
cat << EOF | /usr/local/dovecot/libexec/dovecot/dovecot-lda -d $USER
-o "plugin/quota=maildir:User quota:noenforcing"
From: postmaster at teamgenesys.net	
Subject: quota warning

Your mailbox is now $PERCENT% full.

Please delete unnecessary mail or request more space.

This is an automated message, please do not respond.
EOF


All the users are virtual users and running under vmail id.

I am getting the following error in log file when user reaches 80% of
defined quota limit

Error: quota: net_connect_unix(/usr/local/bin/quota-warning.sh)
failed: Connection refused

Is it configuration issue or anyting else ??

Thanks hoping to get response ....