[Dovecot] pop3 mailbox mirroring issues using dsync

[Nikolaos Milas]

Hello,

I have setup v2.2.12 to mirror mailboxes between our main mail server 
(vmail.example.com) and a failover server (vmail1.example.com).

The problem I have is the behavior of mailboxes used on the main server 
(*vmail*) over POP3. I have setup an IMAP account on the failover server 
(*vmail1*) on such a mailbox: the mailbox is used on vmail using POP3 
and the same is monitored on vmail1 using IMAP. It's mailbox *userx*(in 
Maildir format).

I notice that all mail coming in userx mailbox on vmail, is correctly 
replicated on vmail1, but when it is downloaded from vmail over POP3 
(and the mailbox there remains empty), the same mailbox on vmail1 is not 
updated to be emptied (automatically) as well, but it is accumulating 
mail forever (which is real problem on the mirror server).

Is there a setting to enable correct mirroring of a POP3 mailbox (to 
empty the respective mailbox on the failover server) when mail is 
downloaded from it or something else should be done in this respect?

Please explain.

I quote below the full current config on the main server.

Thanks in advance,
Nick

======================================================================
# 2.2.12: dovecot.conf

protocols = imap pop3

login_greeting = Org POP/IMAP Srv XAPITI XPICTOY

mail_location = maildir:~/Maildir/
mail_gid = 500
mail_uid = 500

auth_mechanisms = plain login
auth_username_format = %Lu

auth_verbose = yes
auth_debug = no

disable_plaintext_auth = no

mail_plugins = quota notify replication

protocol imap {
   imap_client_workarounds = "delay-newmail"
   mail_plugins = quota imap_quota notify replication
}

protocol pop3 {
   mail_max_userip_connections = 3
   mail_plugins = quota notify replication
   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
   pop3_uidl_format = %08Xu%08Xv
}

protocol lda {
   auth_socket_path = /var/run/dovecot/auth-master
   info_log_path =
   log_path =
   mail_plugins = quota notify replication
   postmaster_address = sysadmin at example.com
   sendmail_path = /usr/lib/sendmail
}

userdb {
   args = /etc/dovecot/dovecot-usrdb-ldap.conf
   driver = ldap
}

passdb {
   args = /etc/dovecot/dovecot-passdb-ldap.conf
   driver = ldap
}

dsync_remote_cmd = ssh -l root vmail1.example.com doveadm dsync-server -u%u

plugin {
   mail_replica = remote:vmail at vmail1.example.com
}

plugin {
   quota = maildir:User quota
   quota_rule = *:storage=4G
   quota_rule2 = Trash:storage=+3%%
   quota_warning = storage=75%% quota-warning 75 %u
   quota_warning2 = storage=90%% quota-warning 90 %u
}

service quota-warning {
   executable = script /opt/mail1.sh
   user = vmail
   unix_listener quota-warning {
     user = vmail
   }
}

service aggregator {
   fifo_listener replication-notify-fifo {
     user = vmail
   }
   unix_listener replication-notify {
     user = vmail
   }
}

service replicator {
    unix_listener replicator-doveadm {
      mode = 0600
    }
}

service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
   unix_listener auth-master {
     group = vmail
     mode = 0660
     user = vmail
   }
   user = root
}

service imap-login {
   service_count = 1
   vsz_limit = 64 M
}

service pop3-login {
   service_count = 1
   vsz_limit = 64 M
}

service replicator {
   process_min_avail = 1
}

ssl_ca = </etc/pki/tls/certs/chain-1552.pem
ssl_cert = </etc/pki/tls/certs/cert-1552.pem
ssl_key = </etc/pki/tls/private/key-1552.pem

syslog_facility = local1
======================================================================