Messages lost from imap folders

[Nikolaos Milas]

Hello,

We have one user who is complaining that he has lost mails from 3 imap 
folders, administered through squirrelmail.

The folders suddenly appeared unregistered, and once manually registered 
they were empty.

Has anyone observed something like this?

We are running two servers (as VMs) with Dovecot v2.2.18, synced 
(two-way) using dsync. The configurations follow.

Can you please help me understand what may have gone wrong?

Can I try to find actions regarding these folders in the logs? What 
should I search for?

Could this be an issue involving dsync? How can I trace back dsync 
activity in detail?

Server configs follow (I have only altered the real domain name and the 
login greeting.)

Thanks in advance,
Nick

-----------------------------------------------------------------------------
SERVER 1
-----------------------------------------------------------------------------

protocols = imap pop3

login_greeting = Hello World!

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

auth_mechanisms = plain login
auth_username_format = %Lu

auth_verbose = yes
auth_debug = no
mail_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
replication_dsync_parameters = -d -N -l 30 -U

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

plugin {
   quota = maildir:User quota
   quota_rule = *:storage=5G
   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
}

service imap {
   executable = imap postlogin
}
service pop3 {
   executable = pop3 postlogin
}

service postlogin {
   executable = script-login -d rawlog
   unix_listener postlogin {
   }
}

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

ssl_protocols = !SSLv2 !SSLv3

syslog_facility = local1

-----------------------------------------------------------------------------
SERVER 2
-----------------------------------------------------------------------------

protocols = imap pop3

login_greeting = Hello World!

mail_location = maildir:~/Maildir/
mail_gid = 5000
mail_uid = 5000

auth_mechanisms = plain login
auth_username_format = %Lu
auth_verbose = yes
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 vmail.example.com doveadm dsync-server -u%u
replication_dsync_parameters = -d -N -l 30 -U

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

plugin {
   quota = maildir:User quota
   quota_rule = *:storage=5G
   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-2228.pem
ssl_cert = </etc/pki/tls/certs/cert-2228.pem
ssl_key = </etc/pki/tls/private/key-2228.pem

syslog_facility = local1

ssl_protocols = !SSLv2 !SSLv3

-----------------------------------------------------------------------------