diff --git a/Makefile b/Makefile
index 1570855c..f717e39e 100644
--- a/Makefile
+++ b/Makefile
@@ -25,7 +25,7 @@ clean:
 # remove running and stopped test containers
 	-@ [[ -d config.bak ]] && { rm -rf config ; mv config.bak config ; } || :
 	-@ [[ -d testconfig.bak ]] && { sudo rm -rf test/config ; mv testconfig.bak test/config ; } || :
-	-@ for container in $$(docker ps -a | grep -E "mail|ldap_for_mail|mail_overri.*|hadolint|eclint|shellcheck" | cut -f 1-1 -d ' '); do docker rm -f $$container; done
+	-@ for container in $$(docker ps -a --filter name='^/mail$$|^ldap_for_mail$$|^mail_override_hostname$$|^open-dkim$$|^hadolint$$|^eclint$$|^shellcheck$$' | sed 1d | cut -f 1-1 -d ' '); do docker rm -f $$container; done
 	-@ sudo rm -rf test/onedir test/alias test/quota test/relay test/config/dovecot-lmtp/userdb test/config/key* test/config/opendkim/keys/domain.tld/ test/config/opendkim/keys/example.com/ test/config/opendkim/keys/localdomain2.com/ test/config/postfix-aliases.cf test/config/postfix-receive-access.cf test/config/postfix-receive-access.cfe test/config/dovecot-quotas.cf test/config/postfix-send-access.cf test/config/postfix-send-access.cfe test/config/relay-hosts/chksum test/config/relay-hosts/postfix-aliases.cf test/config/dhparams.pem test/config/dovecot-lmtp/dh.pem test/config/relay-hosts/dovecot-quotas.cf test/config/user-patches.sh test/alias/config/postfix-virtual.cf test/quota/config/dovecot-quotas.cf test/quota/config/postfix-accounts.cf test/relay/config/postfix-relaymap.cf test/relay/config/postfix-sasl-password.cf test/duplicate_configs/
 
 # -----------------------------------------------
diff --git a/target/bin/addmailuser b/target/bin/addmailuser
index 657f56b8..0a0a7f76 100755
--- a/target/bin/addmailuser
+++ b/target/bin/addmailuser
@@ -35,31 +35,41 @@ function __usage
 
 [[ ${1:-} == 'help' ]] && { __usage ; exit 0 ; }
 
-USER="${1}"
+FULL_EMAIL="${1}"
 shift
 PASSWD="${*}"
 
-[[ -z ${USER} ]] && { __usage ; errex 'No username specified' ; }
-[[ "${USER}" =~ .*\@.* ]] || { __usage ; errex 'Username must include the domain' ; }
+[[ -z ${FULL_EMAIL} ]] && { __usage ; errex 'No username specified' ; }
+[[ "${FULL_EMAIL}" =~ .*\@.* ]] || { __usage ; errex 'Username must include the domain' ; }
 
 # Protect config file with lock to avoid race conditions
 touch "${DATABASE}"
-(
-  flock -e 200
+create_lock "$(basename "$0")"
+if grep -qi "^$(escape "${FULL_EMAIL}")|" "${DATABASE}"
+then
+  echo "User '${FULL_EMAIL}' already exists."
+  exit 1
+fi
 
-  if grep -qi "^$(escape "${USER}")|" "${DATABASE}" 2>/dev/null
-  then
-    echo "User '${USER}' already exists."
-    exit 1
-  fi
+if [[ -z ${PASSWD} ]]
+then
+  read -r -s -p "Enter Password: " PASSWD
+  echo
+  [[ -z ${PASSWD} ]] && errex "Password must not be empty"
+fi
 
-  if [[ -z ${PASSWD} ]]
-  then
-    read -r -s -p "Enter Password: " PASSWD
-    echo
-    [[ -z ${PASSWD} ]] && errex "Password must not be empty"
-  fi
+HASH="$(doveadm pw -s SHA512-CRYPT -u "${FULL_EMAIL}" -p "${PASSWD}")"
+echo "${FULL_EMAIL}|${HASH}" >> "${DATABASE}"
 
-  HASH="$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")"
-  echo "${USER}|${HASH}" >> "${DATABASE}"
-) 200< "${DATABASE}"
+USER="${FULL_EMAIL%@*}"
+DOMAIN="${FULL_EMAIL#*@}"
+
+# Tests fail if the creation of /var/mail/${DOMAIN}/${USER} doesn't happen fast enough after addmailuser executes (check-for-changes.sh race-condition)
+if [[ -e "/tmp/docker-mailserver-config-chksum" ]] # Prevent infinite loop in tests like "checking accounts: user3 should have been added to /tmp/docker-mailserver/postfix-accounts.cf even when that file does not exist"
+then
+  while [[ ! -d "/var/mail/${DOMAIN}/${USER}" ]]
+  do
+    echo "Waiting for dovecot to create /var/mail/${DOMAIN}/${USER}..."
+    sleep 1
+  done
+fi
diff --git a/target/bin/delmailuser b/target/bin/delmailuser
index 97c4cb0f..8c2cdbb3 100755
--- a/target/bin/delmailuser
+++ b/target/bin/delmailuser
@@ -86,81 +86,77 @@ then
   fi
 fi
 
-(
-  flock -e 200
+create_lock "$(basename "$0")"
+for EMAIL in "${@}"
+do
+  ERROR=false
 
-  for EMAIL in "${@}"
-  do
-    ERROR=false
+  # very simple plausibility check
+  [[ ${EMAIL} != *@*.* ]] && errex "No valid email address: ${EMAIL}"
 
-    # very simple plausibility check
-    [[ ${EMAIL} != *@*.* ]] && errex "No valid address: ${EMAIL}"
+  USER="${EMAIL%@*}"
+  DOMAIN="${EMAIL#*@}"
 
-    USER="${EMAIL%@*}"
-    DOMAIN="${EMAIL#*@}"
+  # ${EMAIL} must not contain /s and other syntactic characters
+  UNESCAPED_EMAIL="${EMAIL}"
+  EMAIL=$(escape "${EMAIL}")
 
-    # ${EMAIL} must not contain /s and other syntactic characters
-    UNESCAPED_EMAIL="${EMAIL}"
-    EMAIL=$(escape "${EMAIL}")
-
-    if [[ -f ${DATABASE} ]]
+  if [[ -f ${DATABASE} ]]
+  then
+    if ! sed -i "/^${EMAIL}|/d" "${DATABASE}"
     then
-      if ! sed -i "/^${EMAIL}|/d" "${DATABASE}"
-      then
-        echo "${UNESCAPED_EMAIL} couldn't be deleted in ${DATABASE}." >&2
-        ERROR=true
-      fi
-    fi
-
-    if [[ -f ${ALIAS_DATABASE} ]]
-    then
-      # delete all aliases where the user is the only recipient( " ${EMAIL}" )
-      # delete user only for all aliases that deliver to multiple recipients ( ",${EMAIL}" "${EMAIL,}" )
-      if sed -i \
-        -e "/ ${EMAIL}$/d" -e "s/,${EMAIL}//g" -e "s/${EMAIL},//g" \
-        "${ALIAS_DATABASE}"
-      then
-        echo "${UNESCAPED_EMAIL} and potential aliases deleted."
-      else
-        echo "Aliases for ${UNESCAPED_EMAIL} couldn't be deleted in ${ALIAS_DATABASE}." >&2
-        ERROR=true
-      fi
-    fi
-
-    # remove quota directives
-    if [[ -f ${QUOTA_DATABASE} ]]
-    then
-      if ! sed -i -e "/^${EMAIL}:.*$/d" "${QUOTA_DATABASE}"
-      then
-        echo "Quota for ${UNESCAPED_EMAIL} couldn't be deleted in ${QUOTA_DATABASE}." >&2
-      fi
-    fi
-
-    if ! ${MAILDEL}
-    then
-      echo "Leaving the mailbox untouched.
-If you want to delete it at a later point,
-use 'sudo docker exec mailserver rm -R /var/mail/${DOMAIN}/${USER}'"
-      exit 0
-    fi
-
-    if [[ -e "/var/mail/${DOMAIN}/${USER}" ]]
-    then
-      if rm -R "/var/mail/${DOMAIN}/${USER}"
-      then
-        echo "Mailbox deleted."
-      else
-        echo "Mailbox couldn't be deleted." >&2
-        ERROR=true
-      fi
-    else
-      echo "Mailbox directory '/var/mail/${DOMAIN}/${USER}' did not exist." >&2
+      echo "${UNESCAPED_EMAIL} couldn't be deleted in ${DATABASE}." >&2
       ERROR=true
     fi
+  fi
 
-    ${ERROR} && errex 'See the messages above.'
-  done
+  if [[ -f ${ALIAS_DATABASE} ]]
+  then
+    # delete all aliases where the user is the only recipient( " ${EMAIL}" )
+    # delete user only for all aliases that deliver to multiple recipients ( ",${EMAIL}" "${EMAIL,}" )
+    if sed -i \
+      -e "/ ${EMAIL}$/d" -e "s/,${EMAIL}//g" -e "s/${EMAIL},//g" \
+      "${ALIAS_DATABASE}"
+    then
+      echo "${UNESCAPED_EMAIL} and potential aliases deleted."
+    else
+      echo "Aliases for ${UNESCAPED_EMAIL} couldn't be deleted in ${ALIAS_DATABASE}." >&2
+      ERROR=true
+    fi
+  fi
 
-) 200< "${DATABASE}"
+  # remove quota directives
+  if [[ -f ${QUOTA_DATABASE} ]]
+  then
+    if ! sed -i -e "/^${EMAIL}:.*$/d" "${QUOTA_DATABASE}"
+    then
+      echo "Quota for ${UNESCAPED_EMAIL} couldn't be deleted in ${QUOTA_DATABASE}." >&2
+    fi
+  fi
 
+  if ! ${MAILDEL}
+  then
+    echo "Leaving the mailbox untouched.
+If you want to delete it at a later point,
+use 'sudo docker exec mailserver rm -R /var/mail/${DOMAIN}/${USER}'"
+    exit 0
+  fi
+
+  if [[ -e "/var/mail/${DOMAIN}/${USER}" ]]
+  then
+    if rm -R "/var/mail/${DOMAIN}/${USER}"
+    then
+      echo "Mailbox deleted."
+    else
+      echo "Mailbox couldn't be deleted." >&2
+      ERROR=true
+    fi
+    rmdir "/var/mail/${DOMAIN}" 2>/dev/null || true
+  else
+    echo "Mailbox directory '/var/mail/${DOMAIN}/${USER}' did not exist." >&2
+    ERROR=true
+  fi
+
+  ${ERROR} && errex 'See the messages above.'
+done
 exit 0
diff --git a/target/bin/setquota b/target/bin/setquota
index f222c78c..0c6db6bd 100755
--- a/target/bin/setquota
+++ b/target/bin/setquota
@@ -33,24 +33,21 @@ then
 fi
 
 # Protect config file with lock to avoid race conditions
+create_lock "$(basename "$0")"
+
 touch "${DATABASE}"
-(
-  flock -e 200
+if [ -z "${QUOTA}" ]; then
+  read -r -s "Enter quota (e.g. 10M): " QUOTA
+  echo
+  [[ -z "${QUOTA}" ]] && errex "Quota must not be empty. Use 0 for unlimited quota"
+fi
 
-  if [ -z "${QUOTA}" ]; then
-    read -r -s "Enter quota (e.g. 10M): " QUOTA
-    echo
-    [[ -z "${QUOTA}" ]] && errex "Quota must not be empty. Use 0 for unlimited quota"
-  fi
-
-  # check quota
-  if [[ -n ${QUOTA} ]] && ! echo "${QUOTA}" | grep -qE "^([0-9]+(B|k|M|G|T)|0)\$"
-  then
-    usage
-    errex "invalid quota format. e.g. 302M (B (byte), k (kilobyte), M (megabyte), G (gigabyte) or T (terabyte))"
-  fi
-
-  delquota "${USER}"
-  echo "${USER}:${QUOTA}" >>"${DATABASE}"
-) 200< "${DATABASE}"
+# check quota
+if [[ -n ${QUOTA} ]] && ! echo "${QUOTA}" | grep -qE "^([0-9]+(B|k|M|G|T)|0)\$"
+then
+  usage
+  errex "invalid quota format. e.g. 302M (B (byte), k (kilobyte), M (megabyte), G (gigabyte) or T (terabyte))"
+fi
 
+delquota "${USER}"
+echo "${USER}:${QUOTA}" >>"${DATABASE}"
diff --git a/target/bin/updatemailuser b/target/bin/updatemailuser
index c50171ef..bd9efabd 100755
--- a/target/bin/updatemailuser
+++ b/target/bin/updatemailuser
@@ -28,8 +28,7 @@ fi
 HASH="$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")"
 
 # Protect config file with lock to avoid race conditions
-(
-  flock -e 200
-  grep -qi "^$(escape "${USER}")|" "${DATABASE}" 2>/dev/null || errex "User \"${USER}\" does not exist"
-  sed -i "s ^""${USER}""|.* ""${USER}""|""${HASH}"" " "${DATABASE}"
-) 200< "${DATABASE}"
+touch "${DATABASE}"
+create_lock "$(basename "$0")"
+grep -qi "^$(escape "${USER}")|" "${DATABASE}" 2>/dev/null || errex "User \"${USER}\" does not exist"
+sed -i "s ^""${USER}""|.* ""${USER}""|""${HASH}"" " "${DATABASE}"
diff --git a/target/scripts/check-for-changes.sh b/target/scripts/check-for-changes.sh
index f36137e1..f089a5cc 100755
--- a/target/scripts/check-for-changes.sh
+++ b/target/scripts/check-for-changes.sh
@@ -6,7 +6,9 @@
 LOG_DATE=$(date +"%Y-%m-%d %H:%M:%S ")
 _notify 'task' "${LOG_DATE} Start check-for-changes script."
 
-# ? --------------------------------------------- Checks
+SCRIPT_NAME="$(basename "$0")"
+
+# ? ––––––––––––––––––––––––––––––––––––––––––––– Checks
 
 cd /tmp/docker-mailserver || exit 1
 
@@ -43,10 +45,17 @@ while true
 do
   LOG_DATE=$(date +"%Y-%m-%d %H:%M:%S ")
 
+  # Lock configuration while working
+  create_lock "${SCRIPT_NAME}"
+
   # get chksum and check it, no need to lock config yet
   _monitored_files_checksums >"${CHKSUM_FILE}.new"
-
-  if ! cmp --silent -- "${CHKSUM_FILE}" "${CHKSUM_FILE}.new"
+  cmp --silent -- "${CHKSUM_FILE}" "${CHKSUM_FILE}.new"
+  # cmp return codes
+  # 0 – files are identical
+  # 1 – files differ
+  # 2 – inaccessible or missing argument
+  if [ $? -eq 1 ]
   then
     _notify 'inf' "${LOG_DATE} Change detected"
     CHANGED=$(grep -Fxvf "${CHKSUM_FILE}" "${CHKSUM_FILE}.new" | sed 's/^[^ ]\+  //')
@@ -60,178 +69,175 @@ do
     # TODO Perform updates below conditionally too --------
     # Also note that changes are performed in place and are not atomic
     # We should fix that and write to temporary files, stop, swap and start
-    # Lock configuration while working
-    (
-      flock -e 200
 
-      for FILE in ${CHANGED}
-      do
-        case "${FILE}" in
-          "/etc/letsencrypt/acme.json" )
-            for CERTDOMAIN in ${SSL_DOMAIN} ${HOSTNAME} ${DOMAINNAME}
-            do
-              _extract_certs_from_acme "${CERTDOMAIN}" && break
-            done
-            ;;
-
-          * )
-            _notify 'warn' 'File not found for certificate in check_for_changes.sh'
-            ;;
-
-        esac
-      done
-
-      # regenerate postix aliases
-      echo "root: ${PM_ADDRESS}" >/etc/aliases
-      if [[ -f /tmp/docker-mailserver/postfix-aliases.cf ]]
-      then
-        cat /tmp/docker-mailserver/postfix-aliases.cf >>/etc/aliases
-      fi
-      postalias /etc/aliases
-
-      # regenerate postfix accounts
-      : >/etc/postfix/vmailbox
-      : >/etc/dovecot/userdb
-
-      if [[ -f /tmp/docker-mailserver/postfix-accounts.cf ]] && [[ ${ENABLE_LDAP} -ne 1 ]]
-      then
-        sed -i 's/\r//g' /tmp/docker-mailserver/postfix-accounts.cf
-        echo "# WARNING: this file is auto-generated. Modify config/postfix-accounts.cf to edit user list." >/etc/postfix/vmailbox
-
-        # Checking that /tmp/docker-mailserver/postfix-accounts.cf ends with a newline
-        # shellcheck disable=SC1003
-        sed -i -e '$a\' /tmp/docker-mailserver/postfix-accounts.cf
-        chown dovecot:dovecot /etc/dovecot/userdb
-        chmod 640 /etc/dovecot/userdb
-        sed -i -e '/\!include auth-ldap\.conf\.ext/s/^/#/' /etc/dovecot/conf.d/10-auth.conf
-        sed -i -e '/\!include auth-passwdfile\.inc/s/^#//' /etc/dovecot/conf.d/10-auth.conf
-
-        # rebuild relay host
-        if [[ -n ${RELAY_HOST} ]]
-        then
-          # keep old config
-          : >/etc/postfix/sasl_passwd
-          if [[ -n ${SASL_PASSWD} ]]
-          then
-            echo "${SASL_PASSWD}" >>/etc/postfix/sasl_passwd
-          fi
-
-          # add domain-specific auth from config file
-          if [[ -f /tmp/docker-mailserver/postfix-sasl-password.cf ]]
-          then
-            while read -r LINE
-            do
-              if ! grep -q -e "\s*#" <<< "${LINE}"
-              then
-                echo "${LINE}" >>/etc/postfix/sasl_passwd
-              fi
-            done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-sasl-password.cf || true)
-          fi
-
-          # add default relay
-          if [[ -n "${RELAY_USER}" ]] && [[ -n "${RELAY_PASSWORD}" ]]
-          then
-            echo "[${RELAY_HOST}]:${RELAY_PORT}		${RELAY_USER}:${RELAY_PASSWORD}" >>/etc/postfix/sasl_passwd
-          fi
-        fi
-
-        # creating users ; 'pass' is encrypted
-        # comments and empty lines are ignored
-        while IFS=$'|' read -r LOGIN PASS USER_ATTRIBUTES
-        do
-          USER=$(echo "${LOGIN}" | cut -d @ -f1)
-          DOMAIN=$(echo "${LOGIN}" | cut -d @ -f2)
-
-          # test if user has a defined quota
-          if [[ -f /tmp/docker-mailserver/dovecot-quotas.cf ]]
-          then
-            declare -a USER_QUOTA
-            IFS=':' ; read -r -a USER_QUOTA < <(grep "${USER}@${DOMAIN}:" -i /tmp/docker-mailserver/dovecot-quotas.cf)
-            unset IFS
-
-            [[ ${#USER_QUOTA[@]} -eq 2 ]] && USER_ATTRIBUTES="${USER_ATTRIBUTES} userdb_quota_rule=*:bytes=${USER_QUOTA[1]}"
-          fi
-
-          echo "${LOGIN} ${DOMAIN}/${USER}/" >>/etc/postfix/vmailbox
-
-          # user database for dovecot has the following format:
-          # user:password:uid:gid:(gecos):home:(shell):extra_fields
-          # example :
-          # ${LOGIN}:${PASS}:5000:5000::/var/mail/${DOMAIN}/${USER}::userdb_mail=maildir:/var/mail/${DOMAIN}/${USER}
-          echo "${LOGIN}:${PASS}:5000:5000::/var/mail/${DOMAIN}/${USER}::${USER_ATTRIBUTES}" >>/etc/dovecot/userdb
-          mkdir -p "/var/mail/${DOMAIN}/${USER}"
-
-          if [[ -e /tmp/docker-mailserver/${LOGIN}.dovecot.sieve ]]
-          then
-            cp "/tmp/docker-mailserver/${LOGIN}.dovecot.sieve" "/var/mail/${DOMAIN}/${USER}/.dovecot.sieve"
-          fi
-
-          echo "${DOMAIN}" >>/tmp/vhost.tmp
-        done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-accounts.cf)
-      fi
-
-      [[ -n ${RELAY_HOST} ]] && _populate_relayhost_map
-
-
-      if [[ -f /etc/postfix/sasl_passwd ]]
-      then
-        chown root:root /etc/postfix/sasl_passwd
-        chmod 0600 /etc/postfix/sasl_passwd
-      fi
-
-      if [[ -f postfix-virtual.cf ]]
-      then
-        # regenerate postfix aliases
-        : >/etc/postfix/virtual
-        : >/etc/postfix/regexp
-
-        if [[ -f /tmp/docker-mailserver/postfix-virtual.cf ]]
-        then
-          cp -f /tmp/docker-mailserver/postfix-virtual.cf /etc/postfix/virtual
-
-          # the `to` seems to be important; don't delete it
-          # shellcheck disable=SC2034
-          while read -r FROM TO
+    for FILE in ${CHANGED}
+    do
+      case "${FILE}" in
+        "/etc/letsencrypt/acme.json" )
+          for CERTDOMAIN in ${SSL_DOMAIN} ${HOSTNAME} ${DOMAINNAME}
           do
-            UNAME=$(echo "${FROM}" | cut -d @ -f1)
-            DOMAIN=$(echo "${FROM}" | cut -d @ -f2)
+            _extract_certs_from_acme "${CERTDOMAIN}" && break
+          done
+          ;;
 
-            # if they are equal it means the line looks like: "user1	 other@domain.tld"
-            [ "${UNAME}" != "${DOMAIN}" ] && echo "${DOMAIN}" >>/tmp/vhost.tmp
-          done  < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
+        * )
+          _notify 'warn' 'File not found for certificate in check_for_changes.sh'
+          ;;
+
+      esac
+    done
+
+    # regenerate postix aliases
+    echo "root: ${PM_ADDRESS}" >/etc/aliases
+    if [[ -f /tmp/docker-mailserver/postfix-aliases.cf ]]
+    then
+      cat /tmp/docker-mailserver/postfix-aliases.cf >>/etc/aliases
+    fi
+    postalias /etc/aliases
+
+    # regenerate postfix accounts
+    : >/etc/postfix/vmailbox
+    : >/etc/dovecot/userdb
+
+    if [[ -f /tmp/docker-mailserver/postfix-accounts.cf ]] && [[ ${ENABLE_LDAP} -ne 1 ]]
+    then
+      sed -i 's/\r//g' /tmp/docker-mailserver/postfix-accounts.cf
+      echo "# WARNING: this file is auto-generated. Modify config/postfix-accounts.cf to edit user list." >/etc/postfix/vmailbox
+
+      # Checking that /tmp/docker-mailserver/postfix-accounts.cf ends with a newline
+      # shellcheck disable=SC1003
+      sed -i -e '$a\' /tmp/docker-mailserver/postfix-accounts.cf
+      chown dovecot:dovecot /etc/dovecot/userdb
+      chmod 640 /etc/dovecot/userdb
+      sed -i -e '/\!include auth-ldap\.conf\.ext/s/^/#/' /etc/dovecot/conf.d/10-auth.conf
+      sed -i -e '/\!include auth-passwdfile\.inc/s/^#//' /etc/dovecot/conf.d/10-auth.conf
+
+      # rebuild relay host
+      if [[ -n ${RELAY_HOST} ]]
+      then
+        # keep old config
+        : >/etc/postfix/sasl_passwd
+        if [[ -n ${SASL_PASSWD} ]]
+        then
+          echo "${SASL_PASSWD}" >>/etc/postfix/sasl_passwd
         fi
 
-        if [[ -f /tmp/docker-mailserver/postfix-regexp.cf ]]
+        # add domain-specific auth from config file
+        if [[ -f /tmp/docker-mailserver/postfix-sasl-password.cf ]]
         then
-          cp -f /tmp/docker-mailserver/postfix-regexp.cf /etc/postfix/regexp
-          sed -i -e '/^virtual_alias_maps/{
+          while read -r LINE
+          do
+            if ! grep -q -e "\s*#" <<< "${LINE}"
+            then
+              echo "${LINE}" >>/etc/postfix/sasl_passwd
+            fi
+          done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-sasl-password.cf || true)
+        fi
+
+        # add default relay
+        if [[ -n "${RELAY_USER}" ]] && [[ -n "${RELAY_PASSWORD}" ]]
+        then
+          echo "[${RELAY_HOST}]:${RELAY_PORT}		${RELAY_USER}:${RELAY_PASSWORD}" >>/etc/postfix/sasl_passwd
+        fi
+      fi
+
+      # creating users ; 'pass' is encrypted
+      # comments and empty lines are ignored
+      while IFS=$'|' read -r LOGIN PASS USER_ATTRIBUTES
+      do
+        USER=$(echo "${LOGIN}" | cut -d @ -f1)
+        DOMAIN=$(echo "${LOGIN}" | cut -d @ -f2)
+
+        # test if user has a defined quota
+        if [[ -f /tmp/docker-mailserver/dovecot-quotas.cf ]]
+        then
+          declare -a USER_QUOTA
+          IFS=':' ; read -r -a USER_QUOTA < <(grep "${USER}@${DOMAIN}:" -i /tmp/docker-mailserver/dovecot-quotas.cf)
+          unset IFS
+
+          [[ ${#USER_QUOTA[@]} -eq 2 ]] && USER_ATTRIBUTES="${USER_ATTRIBUTES} userdb_quota_rule=*:bytes=${USER_QUOTA[1]}"
+        fi
+
+        echo "${LOGIN} ${DOMAIN}/${USER}/" >>/etc/postfix/vmailbox
+
+        # user database for dovecot has the following format:
+        # user:password:uid:gid:(gecos):home:(shell):extra_fields
+        # example :
+        # ${LOGIN}:${PASS}:5000:5000::/var/mail/${DOMAIN}/${USER}::userdb_mail=maildir:/var/mail/${DOMAIN}/${USER}
+        echo "${LOGIN}:${PASS}:5000:5000::/var/mail/${DOMAIN}/${USER}::${USER_ATTRIBUTES}" >>/etc/dovecot/userdb
+        mkdir -p "/var/mail/${DOMAIN}/${USER}"
+
+        if [[ -e /tmp/docker-mailserver/${LOGIN}.dovecot.sieve ]]
+        then
+          cp "/tmp/docker-mailserver/${LOGIN}.dovecot.sieve" "/var/mail/${DOMAIN}/${USER}/.dovecot.sieve"
+        fi
+
+        echo "${DOMAIN}" >>/tmp/vhost.tmp
+      done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-accounts.cf)
+    fi
+
+    [[ -n ${RELAY_HOST} ]] && _populate_relayhost_map
+
+
+    if [[ -f /etc/postfix/sasl_passwd ]]
+    then
+      chown root:root /etc/postfix/sasl_passwd
+      chmod 0600 /etc/postfix/sasl_passwd
+    fi
+
+    if [[ -f postfix-virtual.cf ]]
+    then
+      # regenerate postfix aliases
+      : >/etc/postfix/virtual
+      : >/etc/postfix/regexp
+
+      if [[ -f /tmp/docker-mailserver/postfix-virtual.cf ]]
+      then
+        cp -f /tmp/docker-mailserver/postfix-virtual.cf /etc/postfix/virtual
+
+        # the `to` seems to be important; don't delete it
+        # shellcheck disable=SC2034
+        while read -r FROM TO
+        do
+          UNAME=$(echo "${FROM}" | cut -d @ -f1)
+          DOMAIN=$(echo "${FROM}" | cut -d @ -f2)
+
+          # if they are equal it means the line looks like: "user1	 other@domain.tld"
+          [ "${UNAME}" != "${DOMAIN}" ] && echo "${DOMAIN}" >>/tmp/vhost.tmp
+        done  < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
+      fi
+
+      if [[ -f /tmp/docker-mailserver/postfix-regexp.cf ]]
+      then
+        cp -f /tmp/docker-mailserver/postfix-regexp.cf /etc/postfix/regexp
+        sed -i -e '/^virtual_alias_maps/{
 s/ regexp:.*//
 s/$/ regexp:\/etc\/postfix\/regexp/
 }' /etc/postfix/main.cf
-        fi
       fi
+    fi
 
-      if [[ -f /tmp/vhost.tmp ]]
-      then
-        sort < /tmp/vhost.tmp | uniq >/etc/postfix/vhost
-        rm /tmp/vhost.tmp
-      fi
+    if [[ -f /tmp/vhost.tmp ]]
+    then
+      sort < /tmp/vhost.tmp | uniq >/etc/postfix/vhost
+      rm /tmp/vhost.tmp
+    fi
 
-      if find /var/mail -maxdepth 3 -a \( \! -user 5000 -o \! -group 5000 \) | read -r
-      then
-        chown -R 5000:5000 /var/mail
-      fi
+    if find /var/mail -maxdepth 3 -a \( \! -user 5000 -o \! -group 5000 \) | read -r
+    then
+      chown -R 5000:5000 /var/mail
+    fi
 
-      supervisorctl restart postfix
+    supervisorctl restart postfix
 
-      # prevent restart of dovecot when smtp_only=1
-      [[ ${SMTP_ONLY} -ne 1 ]] && supervisorctl restart dovecot
-    ) 200<postfix-accounts.cf # end lock
-
-    # mark changes as applied
-    mv "${CHKSUM_FILE}.new" "${CHKSUM_FILE}"
+    # prevent restart of dovecot when smtp_only=1
+    [[ ${SMTP_ONLY} -ne 1 ]] && supervisorctl restart dovecot
   fi
 
+  # mark changes as applied
+  mv "${CHKSUM_FILE}.new" "${CHKSUM_FILE}"
+  remove_lock "${SCRIPT_NAME}"
+
   sleep 1
 done
 
diff --git a/target/scripts/helper-functions.sh b/target/scripts/helper-functions.sh
index 6a8cbf9f..ea2f9f96 100755
--- a/target/scripts/helper-functions.sh
+++ b/target/scripts/helper-functions.sh
@@ -15,7 +15,22 @@ function escape
   echo "${1//./\\.}"
 }
 
-# ? --------------------------------------------- IP & CIDR
+function create_lock
+{
+    SCRIPT_NAME="$1"
+    LOCK_FILE="/tmp/docker-mailserver/${SCRIPT_NAME}.lock"
+    [[ -e "${LOCK_FILE}" ]] && errex "Lock file ${LOCK_FILE} exists. Another $1 execution is happening. Try again later."
+    trap remove_lock EXIT # This won't work if the script is, for example, check-for-changes.sh which uses a while loop to stay running; you'll need to include a remove_lock call at the end of your logic
+    touch "${LOCK_FILE}"
+}
+
+function remove_lock
+{
+  SCRIPT_NAME=${SCRIPT_NAME:-$1}
+  rm -f "/tmp/docker-mailserver/${SCRIPT_NAME}.lock"
+}
+
+# ? ––––––––––––––––––––––––––––––––––––––––––––– IP & CIDR
 
 function _mask_ip_digit
 {
diff --git a/test/linting/lint.sh b/test/linting/lint.sh
index e34cbd1d..74635331 100755
--- a/test/linting/lint.sh
+++ b/test/linting/lint.sh
@@ -6,7 +6,13 @@
 
 SCRIPT="lint.sh"
 
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
+if [[ "$(uname)" == "Darwin" ]]
+then
+  readlink() {
+    greadlink "${@:+$@}" # Requires coreutils
+  }
+fi
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
 REPO_ROOT="$(realpath "${SCRIPT_DIR}"/../../)"
 
 HADOLINT_VERSION=2.4.1
@@ -51,7 +57,7 @@ function __log_success
 
 function __in_path
 {
-  command -v "${@}" &>/dev/null && return 0 ; return 1 ;
+  command -v "${@:+$@}" &>/dev/null && return 0 ; return 1 ;
 }
 
 function _eclint
@@ -142,4 +148,4 @@ function __main
   esac
 }
 
-__main "${@}" || exit ${?}
+__main "${@:+$@}" || exit ${?}