I'm trying to implement the quota warning to users over quota with Dovecot following this tip. I've added the following to my /etc/dovecot/conf.d/30-overquota.conf (any modication in the original /etc/dovecot/dovecot.conf is said would be removed in case of update).plugin {  quota = dict:user::file:/var/vmail/%d/%n/.quotausage  sieve=/var/vmail/%d/%n/.sievequota_warning = storage=50%% quota-warning 50 %uquota_warning2 = storage=80%% quota-warning 80 %uquota_warning3 = -storage=100%% quota-warning below %u # user is no longer over quota}service quota-warning {  executable = script /opt/extra-script/quota-warning.sh  user = root  unix_listener quota-warning {        user = root        mode = 0600  }}then I created the /opt/extra-script/quota-warning.sh, chmodding it to 755#!/bin/shPERCENT=$1USER=$2cat << EOF | /usr/libexec/dovecot/dovecot-lda -d $USER -o plugin/quota=maildir:User quota:noenforcingFrom: noreply@domain.itSubject: Mailbox pienaLa tua casella  piena al $PERCENT%. Cancellare i messaggi vecchi.EOFUnfortunately, this is not working as it should, since I'm not receiving any message on a test mail box of 1MB full at 95% (and the limit in my 30-overquota.conf was set at 50% on line 5). Can anyone help me to configure properly the service? here follows the dovecot -n output which, as far as I can understand, confirms my extra config is included in the running service (but without any desired effect)root@centos1670:~# dovecot -n# 2.2.18: /etc/dovecot/dovecot.conf# Pigeonhole version 0.4.8 (0c4ae064f307+)# OS: Linux 2.6.32-642.15.1.el6.x86_64 x86_64 CentOS release 6.8 (Final) ext3auth_mechanisms = plain login digest-md5 cram-md5 apopauth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890&.-_@'disable_plaintext_auth = nofirst_valid_uid = 30imap_client_workarounds = delay-newmailimap_logout_format = rcvd=%i, sent=%omail_home = /var/qmail/mailnames/%Ld/%Lnmail_location = maildir:/var/qmail/mailnames/%Ld/%Ln/Maildirmail_log_prefix = service=%s, user=%u, ip=[%r]. mail_plugins =  quotamanagesieve_logout_format = rcvd=%i, sent=%omanagesieve_notify_capability = mailtomanagesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate imapflags notifynamespace inbox {  inbox = yes  location =   prefix = INBOX.  separator = .}passdb {  driver = plesk}plugin {  quota = dict:user::file:/var/vmail/%d/%n/.quotausage  quota_grace = 0  quota_warning = storage=50%% quota-warning 50 %u  quota_warning2 = storage=80%% quota-warning 80 %u  quota_warning3 = -storage=100%% quota-warning below %u  sieve = ~/.dovecot.sieve  sieve_dir = ~/sieve  sieve_extensions = +notify +imapflags}pop3_client_workarounds = outlook-no-nuls oe-ns-eohpop3_logout_format = rcvd=%i, sent=%o, top=%t/%p, retr=%r/%b, del=%d/%m, size=%sprotocols = imap pop3 sieveservice auth-worker {  group =   user = }service auth {  group =   unix_listener auth-userdb {    group = popuser    mode = 0600    user = popuser  }  user = }service quota-warning {  executable = script /opt/extra-script/quota-warning.sh  unix_listener quota-warning {    mode = 0600    user = root  }  user = root}ssl_cert = </etc/dovecot/private/ssl-cert-and-key.pemssl_key = </etc/dovecot/private/ssl-cert-and-key.pemuserdb {  args = uid=popuser gid=popuser  driver = static}protocol imap {  mail_plugins =  quota imap_quota}protocol pop3 {  pop3_uidl_format = UID%u-%v}protocol lda {  mail_plugins =  quota sieve}edit: as suggested by Jens Erat, root@centos1670:~# doveadm quota get actually produces the following output:Quota name Type Value Limit %user STORAGE 0 - 0user MESSAGE 0 - 0This seems to denote a defective configuration which might be fixed adding something like quota_rule = *:storage=1GB and enforcing quota recalculation. The problem in doing this is that the Dovecot setup I'm asking about is running under Plesk in which is possible to set different mailbox sizes per user, so the possibility to define the value for quota_rule in a parametric way would be appreciated. 
How to send warning with Dovecot to users when over quota?
dovecot;quota