diff --git a/target/bin/addmailuser b/target/bin/addmailuser
index ef708b4e..e06c04b9 100755
--- a/target/bin/addmailuser
+++ b/target/bin/addmailuser
@@ -46,8 +46,7 @@ touch "${DATABASE}"
 _create_lock # Protect config file with lock to avoid race conditions
 if grep -qi "^$(_escape "${FULL_EMAIL}")|" "${DATABASE}"
 then
-  echo "User '${FULL_EMAIL}' already exists."
-  exit 1
+  _exit_with_error "User '${FULL_EMAIL}' already exists"
 fi
 
 if [[ -z ${PASSWD} ]]
@@ -64,11 +63,11 @@ USER="${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"
+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}..."
+    _log 'info' "Waiting for dovecot to create '/var/mail/${DOMAIN}/${USER}/'"
     sleep 1
   done
 fi
diff --git a/target/bin/delalias b/target/bin/delalias
index 0a0ecbf2..c427ed95 100755
--- a/target/bin/delalias
+++ b/target/bin/delalias
@@ -12,8 +12,8 @@ function __usage { echo "Usage: delalias <alias@domain> <recipient@other>" ; }
 
 [[ ${1:-} == 'help' ]] && { __usage ; exit 0 ; }
 
-[[ -z ${EMAIL} ]] && { __usage ; _exit_with_error "Error: No alias specified" ; }
-[[ -z ${RECIPIENT} ]] && { __usage ; _exit_with_error "Error: No recipient specified" ; }
+[[ -z ${EMAIL} ]] && { __usage ; _exit_with_error 'No alias specified' ; }
+[[ -z ${RECIPIENT} ]] && { __usage ; _exit_with_error 'No recipient specified' ; }
 [[ -s ${DATABASE} ]] || exit 0
 
 sed -i \
diff --git a/target/bin/delmailuser b/target/bin/delmailuser
index 8c5ad727..9f78b158 100755
--- a/target/bin/delmailuser
+++ b/target/bin/delmailuser
@@ -55,31 +55,31 @@ fi
 
 while getopts ":yYh" OPT
 do
-  case ${OPT} in
-    y | Y )
+  case "${OPT}" in
+    ( 'y' | 'Y' )
       MAILDEL=true
       ;;
 
-    h )
+    ( 'h' )
       __usage
       exit 0
       ;;
 
-    * )
+    ( * )
       __usage
-      _exit_with_error "The option ${OPT} is unknown."
+      _exit_with_error "The option '${OPT}' is unknown"
       ;;
 
   esac
 done
 shift $((OPTIND-1))
 
-[[ -z ${*} ]] && { __usage ; _exit_with_error "No user specifed" ; }
+[[ -z ${*} ]] && { __usage ; _exit_with_error 'No user specified' ; }
 [[ -s ${DATABASE} ]] || exit 0
 
 if ! ${MAILDEL}
 then
-  read -r -p "Do you want to delete the mailbox as well (removing all mails) ? [Y/n] " MAILDEL_CHOSEN
+  read -r -p "Do you want to delete the mailbox as well (removing all mails)? [Y/n] " MAILDEL_CHOSEN
   if [[ ${MAILDEL_CHOSEN} =~ (y|Y|yes|Yes) ]] || [[ -z ${MAILDEL_CHOSEN} ]]
   then
     MAILDEL=true
@@ -103,7 +103,7 @@ do
   then
     if ! sedfile --strict -i "/^${EMAIL}|/d" "${DATABASE}"
     then
-      echo "${UNESCAPED_EMAIL} couldn't be deleted in ${DATABASE}." >&2
+      _log 'error' "'${UNESCAPED_EMAIL}' couldn't be deleted in '${DATABASE}'"
       ERROR=true
     fi
   fi
@@ -116,9 +116,9 @@ do
       -e "/ ${EMAIL}$/d" -e "s/,${EMAIL}//g" -e "s/${EMAIL},//g" \
       "${ALIAS_DATABASE}"
     then
-      echo "${UNESCAPED_EMAIL} and potential aliases deleted."
+      _log 'info' "'${UNESCAPED_EMAIL}' and potential aliases deleted"
     else
-      echo "Aliases for ${UNESCAPED_EMAIL} couldn't be deleted in ${ALIAS_DATABASE}." >&2
+      _log 'error' "Aliases for '${UNESCAPED_EMAIL}' couldn't be deleted in '${ALIAS_DATABASE}'"
       ERROR=true
     fi
   fi
@@ -128,7 +128,7 @@ do
   then
     if ! sedfile --strict -i -e "/^${EMAIL}:.*$/d" "${QUOTA_DATABASE}"
     then
-      echo "Quota for ${UNESCAPED_EMAIL} couldn't be deleted in ${QUOTA_DATABASE}." >&2
+      _log 'warn' "Quota for '${UNESCAPED_EMAIL}' couldn't be deleted in '${QUOTA_DATABASE}'"
     fi
   fi
 
@@ -144,17 +144,18 @@ use 'sudo docker exec mailserver rm -R /var/mail/${DOMAIN}/${USER}'"
   then
     if rm -R "/var/mail/${DOMAIN}/${USER}"
     then
-      echo "Mailbox deleted."
+      _log 'info' 'Mailbox deleted'
     else
-      echo "Mailbox couldn't be deleted." >&2
+      _log 'error' 'Mailbox could not be deleted'
       ERROR=true
     fi
-    rmdir "/var/mail/${DOMAIN}" 2>/dev/null || true
+    rmdir "/var/mail/${DOMAIN}" &>/dev/null
   else
-    echo "Mailbox directory '/var/mail/${DOMAIN}/${USER}' did not exist." >&2
+    log 'error' "Mailbox directory '/var/mail/${DOMAIN}/${USER}' did not exist"
     ERROR=true
   fi
 
   ${ERROR} && _exit_with_error 'See the messages above.'
 done
+
 exit 0
diff --git a/target/bin/delquota b/target/bin/delquota
index 388c9c9f..b553acbe 100755
--- a/target/bin/delquota
+++ b/target/bin/delquota
@@ -6,20 +6,16 @@ source /usr/local/bin/helpers/index.sh
 DATABASE=${DATABASE:-/tmp/docker-mailserver/dovecot-quotas.cf}
 USER_DATABASE=${USER_DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-function __usage { echo "Usage: delquota <username@domain>" ; }
+function __usage { echo 'Usage: delquota <username@domain>' ; }
 
 [[ ${1:-} == 'help' ]] && { __usage ; exit 0 ; }
 
 USER="${1}"
 
-[[ -z ${USER} ]]  && { __usage ; _exit_with_error "No username specified" ; }
-[[ ${USER} =~ .*\@.* ]] || { __usage ; _exit_with_error "Username must include the domain"; }
+[[ -z ${USER} ]] && { __usage ; _exit_with_error 'No username specified' ; }
+[[ ${USER} =~ .*\@.* ]] || { __usage ; _exit_with_error 'Username must include the domain' ; }
 
-if ! grep -qE "^${USER}\|" "${USER_DATABASE}"
-then
-  __usage
-  _exit_with_error "user ${USER} does not exist"
-fi
+grep -qE "^${USER}\|" "${USER_DATABASE}" || _exit_with_error "User '${USER}' does not exist"
 
 [[ -s ${DATABASE} ]] || exit 0
 
diff --git a/target/bin/excluderelaydomain b/target/bin/excluderelaydomain
index f86c6c8c..50d93c06 100755
--- a/target/bin/excluderelaydomain
+++ b/target/bin/excluderelaydomain
@@ -7,9 +7,9 @@ DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-relaymap.cf}
 
 DOMAIN="${1}"
 
-function usage { echo "Usage: excluderelayhost <domain>" ; }
+function __usage { echo 'Usage: excluderelayhost <domain>' ; }
 
-[[ -z ${DOMAIN} ]] && { usage ; _exit_with_error "no domain specified" ; }
+[[ -z ${DOMAIN} ]] && { __usage ; _exit_with_error "no domain specified" ; }
 
 if grep -qi "^@${DOMAIN}" "${DATABASE}" 2>/dev/null
 then
diff --git a/target/bin/fail2ban b/target/bin/fail2ban
index 58f2b6a7..7e97a73a 100755
--- a/target/bin/fail2ban
+++ b/target/bin/fail2ban
@@ -5,7 +5,9 @@ source /usr/local/bin/helpers/index.sh
 
 if ! IPTABLES_OUTPUT=$(iptables -L -n 2>&1)
 then
-  echo "IPTables is not functioning correctly. The output of \`iptables -L\` was:
+  _exit_with_error "IPTables is not functioning correctly
+
+The output of \`iptables -L\` was:
 
 ${IPTABLES_OUTPUT}
 
@@ -14,14 +16,10 @@ Possible causes for this error are
 1. Missing capabilities (you need CAP_NET_RAW & CAP_NET_ADMIN, see \`capsh --print\`)
 2. Modifications caused by user-patches.sh
 3. Host is configured incorrectly
-
-Aborting...
 "
-
-  exit 1
 fi
 
-function usage { echo "Usage: ${0} [<unban> <ip-address>]" ; }
+function __usage { echo "Usage: ${0} [<unban> <ip-address>]" ; }
 
 unset JAILS
 declare -a JAILS
@@ -48,14 +46,14 @@ then
 
   if [[ ${IP_COUNT} -eq 0 ]]
   then
-    echo "No IPs have been banned."
+    _log 'info' 'No IPs have been banned'
   fi
 
 else
 
-  case ${1} in
+  case "${1}" in
 
-    unban)
+    ( 'unban' )
       shift
       if [[ -n ${1} ]]
       then
@@ -68,14 +66,14 @@ else
         done
 
       else
-        echo "You need to specify an IP address. Run './setup.sh debug fail2ban' to get a list of banned IP addresses." >&2
+        _log 'warn' "You need to specify an IP address: Run './setup.sh debug fail2ban' to get a list of banned IP addresses"
         exit 0
       fi
       ;;
 
-    *)
-      usage
-      _exit_with_error "unknown command: ${1}"
+    ( * )
+      __usage
+      _exit_with_error "Unknown command '${1}'"
       ;;
 
   esac
diff --git a/target/bin/fetchmailrc_split b/target/bin/fetchmailrc_split
index d0edb1ea..1f15ad2d 100755
--- a/target/bin/fetchmailrc_split
+++ b/target/bin/fetchmailrc_split
@@ -14,7 +14,7 @@ DEFAULT_FILE="${FETCHMAILRCD}/defaults"
 
 if [[ ! -r "${FETCHMAILRC}" ]]
 then
-  echo "Error: File ${FETCHMAILRC} not found"
+  _log 'error' "File '${FETCHMAILRC}' not found"
   exit 1
 fi
 
@@ -22,7 +22,7 @@ if [[ ! -d ${FETCHMAILRCD} ]]
 then
   if ! mkdir "${FETCHMAILRCD}"
   then
-    echo "Error: Unable to create folder ${FETCHMAILRCD}"
+    _log 'error' "Unable to create folder '${FETCHMAILRCD}'"
     exit 1
   fi
 fi
diff --git a/target/bin/listalias b/target/bin/listalias
index cc4b371a..fcdf1e5d 100755
--- a/target/bin/listalias
+++ b/target/bin/listalias
@@ -5,8 +5,8 @@ source /usr/local/bin/helpers/index.sh
 
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-virtual.cf}
 
-[[ -f ${DATABASE} ]] || _exit_with_error "Error: No postfix-virtual.cf file"
-[[ -s ${DATABASE} ]] || _exit_with_error "Error: Empty postfix-virtual.cf - no aliases have been added"
+[[ -f ${DATABASE} ]] || _exit_with_error "No 'postfix-virtual.cf' file"
+[[ -s ${DATABASE} ]] || _exit_with_error "Empty 'postfix-virtual.cf' - no aliases have been added"
 
 grep -v "^\s*$\|^\s*\#" "${DATABASE}"
 exit 0
diff --git a/target/bin/listmailuser b/target/bin/listmailuser
index 46a59730..83343c3a 100755
--- a/target/bin/listmailuser
+++ b/target/bin/listmailuser
@@ -7,7 +7,7 @@ source /usr/local/bin/helpers/index.sh
 # shellcheck source=/dev/null
 source /etc/dms-settings 2>/dev/null
 
-function dovecot_quota_to_hr()
+function dovecot_quota_to_hr
 {
   if [[ ${1:-} == "-" ]]
   then
@@ -16,15 +16,15 @@ function dovecot_quota_to_hr()
   then
     echo $(( 1024 * ${1} )) | numfmt --to=iec
   else
-    notify 'err' "Supplied non-number argument '${1:-}' to 'dovecot_quota_to_hr()' in script 'listmailuser'"
+    _exit_with_error "Supplied non-number argument '${1:-}' to 'dovecot_quota_to_hr()' in script 'listmailuser'"
   fi
 }
 
-DATABASE="/tmp/docker-mailserver/postfix-accounts.cf"
-ALIASES="/tmp/docker-mailserver/postfix-virtual.cf"
+DATABASE='/tmp/docker-mailserver/postfix-accounts.cf'
+ALIASES='/tmp/docker-mailserver/postfix-virtual.cf'
 
-[[ -f ${DATABASE} ]] || _exit_with_error "Error: No postfix-accounts.cf file"
-[[ -s ${DATABASE} ]] || _exit_with_error "Error: Empty postfix-accounts.cf - no accounts have been added"
+[[ -f ${DATABASE} ]] || _exit_with_error "No 'postfix-accounts.cf' file"
+[[ -s ${DATABASE} ]] || _exit_with_error "Empty 'postfix-accounts.cf' - no accounts have been added"
 
 while read -r LINE
 do
diff --git a/target/bin/open-dkim b/target/bin/open-dkim
index b72e9127..6d7f3d62 100755
--- a/target/bin/open-dkim
+++ b/target/bin/open-dkim
@@ -1,5 +1,8 @@
 #! /bin/bash
 
+# shellcheck source=../scripts/helpers/index.sh
+source /usr/local/bin/helpers/index.sh
+
 KEYSIZE=4096
 SELECTOR=mail
 DOMAINS=
@@ -52,48 +55,44 @@ function __usage
 
 while [[ ${#} -gt 0 ]]
 do
-  case ${1} in
-    keysize )
-      if [[ -n ${2+'set'} ]]
+  case "${1}" in
+    ( 'keysize' )
+      if [[ -n ${2+set} ]]
       then
         KEYSIZE="${2}"
         shift
         shift
       else
-        echo "No keysize provided after 'keysize' argument. Aborting." >&2
-        exit 2
+        _exit_with_error "No keysize provided after 'keysize' argument"
       fi
       ;;
 
-    selector )
-      if [[ -n ${2+'set'} ]]
+    ( 'selector' )
+      if [[ -n ${2+set} ]]
       then
         # shellcheck disable=SC2034
         SELECTOR="${2}"
         shift
         shift
       else
-        echo "No selector provided after 'selector' argument. Aborting." >&2
-        exit 2
+        _exit_with_error "No selector provided after 'selector' argument"
       fi
       ;;
 
-    domain )
-      if [[ -n ${2+'set'} ]]
+    ( 'domain' )
+      if [[ -n ${2+set} ]]
       then
         DOMAINS="${2}"
         shift
         shift
       else
-        echo "No domain(s) provided after 'domain' argument. Aborting." >&2
-        exit 2
+        _exit_with_error "No domain(s) provided after 'domain' argument"
       fi
       ;;
 
-    * )
+    ( * )
       __usage
-      echo -e "\nUnknown options ${1} ${2:-}. Aborting." >&2
-      exit 2
+      _exit_with_error "Unknown options '${1}' ${2:+and \'${2}\'}"
       ;;
 
   esac
@@ -127,7 +126,7 @@ then
     done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
   fi
 else
-  tr ',' '\n' <<< "${DOMAINS}" > /tmp/vhost.dkim.tmp
+  tr ',' '\n' <<< "${DOMAINS}" >/tmp/vhost.dkim.tmp
 fi
 
 sort < /tmp/vhost.dkim.tmp | uniq >/tmp/vhost
@@ -135,7 +134,7 @@ rm /tmp/vhost.dkim.tmp
 
 if [[ ! -s /tmp/vhost ]]
 then
-  echo "No entries found, no keys to make."
+  _log 'warn' 'No entries found, no keys to make'
   exit 0
 fi
 
@@ -145,7 +144,7 @@ do
 
   if [[ ! -f "/tmp/docker-mailserver/opendkim/keys/${DKIM_DOMAIN}/${SELECTOR}.private" ]]
   then
-    echo "Creating DKIM private key /tmp/docker-mailserver/opendkim/keys/${DKIM_DOMAIN}/${SELECTOR}.private"
+    _log 'info' "Creating DKIM private key '/tmp/docker-mailserver/opendkim/keys/${DKIM_DOMAIN}/${SELECTOR}.private'"
 
     opendkim-genkey \
       --bits="${KEYSIZE}" \
@@ -159,7 +158,7 @@ do
   KEYTABLEENTRY="${SELECTOR}._domainkey.${DKIM_DOMAIN} ${DKIM_DOMAIN}:${SELECTOR}:/etc/opendkim/keys/${DKIM_DOMAIN}/${SELECTOR}.private"
   if [[ ! -f "/tmp/docker-mailserver/opendkim/KeyTable" ]]
   then
-    echo "Creating DKIM KeyTable"
+    _log 'debug' 'Creating DKIM KeyTable'
     echo "${KEYTABLEENTRY}" >/tmp/docker-mailserver/opendkim/KeyTable
   else
     if ! grep -q "${KEYTABLEENTRY}" "/tmp/docker-mailserver/opendkim/KeyTable"
@@ -172,7 +171,7 @@ do
   SIGNINGTABLEENTRY="*@${DKIM_DOMAIN} ${SELECTOR}._domainkey.${DKIM_DOMAIN}"
   if [[ ! -f /tmp/docker-mailserver/opendkim/SigningTable ]]
   then
-    echo "Creating DKIM SigningTable"
+    _log 'debug' 'Creating DKIM SigningTable'
     echo "*@${DKIM_DOMAIN} ${SELECTOR}._domainkey.${DKIM_DOMAIN}" >/tmp/docker-mailserver/opendkim/SigningTable
   else
     if ! grep -q "${SIGNINGTABLEENTRY}" /tmp/docker-mailserver/opendkim/SigningTable
@@ -185,7 +184,7 @@ done < <(grep -vE '^(\s*$|#)' /tmp/vhost)
 # create TrustedHosts if missing
 if [[ -d /tmp/docker-mailserver/opendkim ]] && [[ ! -f /tmp/docker-mailserver/opendkim/TrustedHosts ]]
 then
-  echo "Creating DKIM TrustedHosts"
+  _log 'debug' 'Creating DKIM TrustedHosts'
   echo "127.0.0.1" >/tmp/docker-mailserver/opendkim/TrustedHosts
   echo "localhost" >>/tmp/docker-mailserver/opendkim/TrustedHosts
 fi
diff --git a/target/bin/postfix-summary b/target/bin/postfix-summary
index b049a00c..df0f11f3 100755
--- a/target/bin/postfix-summary
+++ b/target/bin/postfix-summary
@@ -7,7 +7,7 @@ HOSTNAME=${1}
 RECIPIENT=${2}
 SENDER=${3}
 
-[[ -x /usr/sbin/pflogsumm ]] || _exit_with_error "Critical: /usr/sbin/pflogsumm not found"
+[[ -x /usr/sbin/pflogsumm ]] || _exit_with_error "'/usr/sbin/pflogsumm' not found or executable"
 
 # The case that the mail.log.1 file isn't readable shouldn't
 # actually be possible with logrotate not rotating empty files..
diff --git a/target/bin/report-pflogsumm-yesterday b/target/bin/report-pflogsumm-yesterday
index cb7b6818..291e7a0d 100755
--- a/target/bin/report-pflogsumm-yesterday
+++ b/target/bin/report-pflogsumm-yesterday
@@ -11,7 +11,7 @@ HOSTNAME=${1}
 RECIPIENT=${2}
 SENDER=${3}
 
-[[ -x /usr/sbin/pflogsumm ]] || _exit_with_error "Critical: /usr/sbin/pflogsumm not found"
+[[ -x /usr/sbin/pflogsumm ]] || _exit_with_error "'/usr/sbin/pflogsumm' not found or executable"
 
 # shellcheck disable=SC2046
 BODY=$(gzip -cdfq $(ls -tr /var/log/mail/mail.log*) | /usr/sbin/pflogsumm --problems_first -d yesterday)
diff --git a/target/bin/restrict-access b/target/bin/restrict-access
index c7fbaa8c..19f430da 100755
--- a/target/bin/restrict-access
+++ b/target/bin/restrict-access
@@ -6,33 +6,36 @@ source /usr/local/bin/helpers/index.sh
 MODE="${1}"
 USER="${3}"
 
-function usage  {	echo "Usage: ${0} <add|del|list> <send|receive> [<email@domain.com>]" ; }
+function __usage { echo "Usage: ${0} <add|del|list> <send|receive> [<email@domain.com>]" ; }
 
-[[ -z ${MODE} ]] && _exit_with_error "missing parameters: <add|del|list> <send|receive> [<email@domain.com>]"
+[[ -z ${MODE} ]] && _exit_with_error 'Missing parameters: <add|del|list> <send|receive> [<email@domain.com>]'
 
-case ${2} in
-  send)
+case "${2}" in
+  ( 'send' )
     DATABASE="/tmp/docker-mailserver/postfix-send-access.cf"
     ;;
-  receive)
+
+  ( 'receive' )
     DATABASE="/tmp/docker-mailserver/postfix-receive-access.cf"
     ;;
-  *)
-    usage
-    _exit_with_error "missing parameters. Specify \"send\" or \"receive\""
+
+  ( * )
+    __usage
+    _exit_with_error "Missing parameters: specify 'send' or 'receive'"
     ;;
+
 esac
 
 if [[ -z ${USER} ]] && [[ ${MODE} != list ]]
 then
-  read -r -p "User(user@domain.com): " USER
+  read -r -p 'User(user@domain.com): ' USER
   echo
-  [[ -z ${USER} ]] && _exit_with_error "User must not be empty"
+  [[ -z ${USER} ]] && _exit_with_error 'User must not be empty'
 fi
 
-case ${MODE} in
-  add)
-    grep -qi "^$(_escape "${USER}")" "${DATABASE}" 2>/dev/null && _exit_with_error "User \"${USER}\" already denied to ${2} mails"
+case "${MODE}" in
+  ( 'add' )
+    grep -qi "^$(_escape "${USER}")" "${DATABASE}" 2>/dev/null && _exit_with_error "User '${USER}' already denied to ${2} mails"
 
     if [[ ! -f ${DATABASE} ]]
     then
@@ -45,18 +48,19 @@ case ${MODE} in
     fi
 
     echo -e "${USER} \t\t REJECT" >>"${DATABASE}"
-  ;;
-
-  del)
-    sed -ie "/^$(_escape "${USER}")/d" "${DATABASE}" 2>/dev/null || _exit_with_error "User \"${USER}\" not found."
-  ;;
-
-  list)
-    grep "REJECT" "${DATABASE}" 2>/dev/null || echo "Everyone is allowed to ${2} mails."
     ;;
-  *)
-    usage
-    _exit_with_error "missing mode. Specify \"add\", \"del\" or \"list\""
-  ;;
+
+  ( 'del' )
+    sed -ie "/^$(_escape "${USER}")/d" "${DATABASE}" 2>/dev/null || _exit_with_error "User '${USER}' not found."
+    ;;
+
+  ( 'list' )
+    grep "REJECT" "${DATABASE}" 2>/dev/null || _log 'info' "Everyone is allowed to ${2} mails"
+    ;;
+
+  ( * )
+    __usage
+    _exit_with_error "Missing mode: specify 'add', 'del' or 'list'"
+    ;;
 
 esac
diff --git a/target/bin/sedfile b/target/bin/sedfile
index 7f8e9c6b..3b849e07 100755
--- a/target/bin/sedfile
+++ b/target/bin/sedfile
@@ -11,19 +11,21 @@
 
 set -ueo pipefail
 
-HASHTOOL="sha1sum"
+function __usage { echo "Usage: ${0} -i <replace/delete operation> <file>" ; }
+
+HASHTOOL='sha1sum'
 SKIP_ERROR=0
 
-if [[ $# -lt 3 ]]
+if [[ ${#} -lt 3 ]]
 then
-  echo "Error:  At least, three parameters must be given."
-  echo "Syntax: sedfile -i <replace/delete operation> <file>"
+  echo 'Error: At least three parameters must be given'
+  __usage
   echo
   exit 1
 fi >&2
 
-[[ -f /CONTAINER_START ]] && SKIP_ERROR=1 # Hide error, if container was restarted.
-if [[ "${1}" == "--strict" ]]         # Show error every time.
+[[ -f /CONTAINER_START ]] && SKIP_ERROR=1 # hide error if container was restarted
+if [[ ${1} == '--strict' ]]               # show error every time
 then
   SKIP_ERROR=0
   shift
@@ -33,14 +35,14 @@ fi
 FILE=${*: -1}
 
 OLD=$(${HASHTOOL} "${FILE}")
-sed "$@"
+sed "${@}"
 NEW=$(${HASHTOOL} "${FILE}")
 
 # fail if file was not modified
 if [[ ${OLD} == "${NEW}" ]] && [[ ${SKIP_ERROR} -eq 0 ]]
 then
-  echo "Error: sed $*"
+  echo "Error: No difference after call to 'sed' in 'sedfile' (sed ${*})" >&2
   exit 1
-fi >&2
+fi
 
 exit 0
diff --git a/target/bin/setquota b/target/bin/setquota
index 9fd6ee5e..334216aa 100755
--- a/target/bin/setquota
+++ b/target/bin/setquota
@@ -15,39 +15,29 @@ USER="${1}"
 shift
 QUOTA="${*}"
 
-function usage  { echo "Usage: setquota <user@domain> [<quota>]" ; }
+function __usage { echo 'Usage: setquota <user@domain> [<quota>]' ; }
 
-[[ -z ${USER} ]] && { usage ; _exit_with_error "no username specified" ; }
-[[ ${USER} =~ .*\@.* ]] || { usage ; _exit_with_error "username must include the domain" ; }
+[[ -z ${USER} ]] && { __usage ; _exit_with_error "No username specified" ; }
+[[ ${USER} =~ .*\@.* ]] || { __usage ; _exit_with_error "Username must include the domain" ; }
 
-if ! grep -qE "^${USER}\|" "${USER_DATABASE}"
+grep -qE "^${USER}\|" "${USER_DATABASE}" || _exit_with_error "User '${USER}' does not exist"
+
+if [[ -z ${QUOTA} ]]
 then
-  usage; _exit_with_error "user ${USER} does not exist"
+  read -r -s 'Enter quota (e.g. 10M): ' QUOTA
+  echo
+  [[ -z "${QUOTA}" ]] && _exit_with_error '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)\$"
+if ! grep -qE "^([0-9]+(B|k|M|G|T)|0)\$" <<< "${QUOTA}"
 then
-  usage
-  _exit_with_error "invalid quota format. e.g. 302M (B (byte), k (kilobyte), M (megabyte), G (gigabyte) or T (terabyte))"
+  __usage
+  _exit_with_error 'Invalid quota format. e.g. 302M (B (byte), k (kilobyte), M (megabyte), G (gigabyte) or T (terabyte))'
 fi
 
 _create_lock # Protect config file with lock to avoid race conditions
-
 touch "${DATABASE}"
-if [[ -z ${QUOTA} ]]
-then
-  read -r -s "Enter quota (e.g. 10M): " QUOTA
-  echo
-  [[ -z "${QUOTA}" ]] && _exit_with_error "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
-  _exit_with_error "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 7234a438..81374748 100755
--- a/target/bin/updatemailuser
+++ b/target/bin/updatemailuser
@@ -14,15 +14,15 @@ USER="${1}"
 shift
 PASSWD="${*}"
 
-function usage  {	echo "Usage: updatemailuser <user@domain.tld> [password]" ; }
+function __usage { echo 'Usage: updatemailuser <user@domain.tld> [password]' ; }
 
-[[ -z ${USER} ]] && { usage ; _exit_with_error "no username specified" ; }
+[[ -z ${USER} ]] && { __usage ; _exit_with_error 'No username specified' ; }
 
 if [[ -z ${PASSWD} ]]
 then
-  read -r -s -p "Enter Password: " PASSWD
+  read -r -s -p 'Enter Password: ' PASSWD
   echo
-  [[ -z ${PASSWD} ]] && _exit_with_error "Password must not be empty"
+  [[ -z ${PASSWD} ]] && _exit_with_error 'Password must not be empty'
 fi
 
 HASH="$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")"
diff --git a/target/scripts/helpers/lock.sh b/target/scripts/helpers/lock.sh
index 76ba482f..a8fef039 100644
--- a/target/scripts/helpers/lock.sh
+++ b/target/scripts/helpers/lock.sh
@@ -24,17 +24,17 @@ function _create_lock
   done
   trap _remove_lock EXIT
 
-  _log 'trace' "Creating lock ${LOCK_FILE}"
+  _log 'trace' "Creating lock '${LOCK_FILE}'"
   echo "${LOCK_ID}" >"${LOCK_FILE}"
 }
 
 function _remove_lock
 {
   LOCK_FILE="${LOCK_FILE:-"/tmp/docker-mailserver/${SCRIPT_NAME}.lock"}"
-  [[ -z "${LOCK_ID}" ]] && _exit_with_error "Cannot remove ${LOCK_FILE} as there is no LOCK_ID set"
+  [[ -z "${LOCK_ID}" ]] && _exit_with_error "Cannot remove '${LOCK_FILE}' as there is no LOCK_ID set"
   if [[ -e "${LOCK_FILE}" ]] && grep -q "${LOCK_ID}" "${LOCK_FILE}" # Ensure we don't delete a lock that's not ours
   then
     rm -f "${LOCK_FILE}"
-    _log 'trace' "Removed lock ${LOCK_FILE}"
+    _log 'trace' "Removed lock '${LOCK_FILE}'"
   fi
 }
diff --git a/test/mail_fail2ban.bats b/test/mail_fail2ban.bats
index e4c255be..bb1c6df8 100644
--- a/test/mail_fail2ban.bats
+++ b/test/mail_fail2ban.bats
@@ -140,7 +140,7 @@ function teardown_file() {
   assert_output --partial "Unbanned IP from dovecot: 1"
 
   run ./setup.sh -c mail_fail2ban debug fail2ban unban
-  assert_output --partial "You need to specify an IP address. Run"
+  assert_output --partial "You need to specify an IP address: Run"
 }
 
 #
diff --git a/test/open_dkim.bats b/test/open_dkim.bats
index 32a8d4ca..b6bc7cac 100644
--- a/test/open_dkim.bats
+++ b/test/open_dkim.bats
@@ -4,7 +4,7 @@ export IMAGE_NAME CONTAINER_NAME TEST_FILE
 
 IMAGE_NAME="${NAME:?Image name must be set}"
 CONTAINER_NAME='open-dkim'
-TEST_FILE='OpenDKIM :: '
+TEST_FILE='checking OpenDKIM: '
 
 # WHY IS THIS CONTAINER EVEN CREATED WHEN MOST TESTS DO NOT USE IT?
 function setup_file
@@ -20,6 +20,7 @@ function setup_file
 		-e DEFAULT_RELAY_HOST=default.relay.host.invalid:25 \
 		-e PERMIT_DOCKER=host \
 		-e DMS_DEBUG=0 \
+		-e LOG_LEVEL='trace' \
 		-h mail.my-domain.com \
     -t "${IMAGE_NAME}"
 
@@ -69,6 +70,7 @@ function teardown_file
   mkdir -p "${PRIVATE_CONFIG}/keyDefault"
 
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/keyDefault/":/tmp/docker-mailserver/ \
     -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
     -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
@@ -98,6 +100,7 @@ function teardown_file
     mkdir -p "${PRIVATE_CONFIG}/config/key4096"
 
     run docker run --rm \
+      -e LOG_LEVEL='trace' \
       -v "${PRIVATE_CONFIG}/key2048/":/tmp/docker-mailserver/ \
       -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
       -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
@@ -126,6 +129,7 @@ function teardown_file
     mkdir -p "${PRIVATE_CONFIG}/config/key2048"
 
     run docker run --rm \
+      -e LOG_LEVEL='trace' \
       -v "${PRIVATE_CONFIG}/key2048/":/tmp/docker-mailserver/ \
       -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
       -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
@@ -154,6 +158,7 @@ function teardown_file
     mkdir -p "${PRIVATE_CONFIG}/key1024"
 
     run docker run --rm \
+      -e LOG_LEVEL='trace' \
       -v "${PRIVATE_CONFIG}/key1024/":/tmp/docker-mailserver/ \
       -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
       -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
@@ -176,6 +181,7 @@ function teardown_file
   rm -rf "${PRIVATE_CONFIG}/empty"
   mkdir -p "${PRIVATE_CONFIG}/empty"
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/empty/":/tmp/docker-mailserver/ \
     -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
     -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
@@ -211,6 +217,7 @@ function teardown_file
   rm -rf "${PRIVATE_CONFIG}/without-accounts"
   mkdir -p "${PRIVATE_CONFIG}/without-accounts"
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-accounts/":/tmp/docker-mailserver/ \
     -v "${PRIVATE_CONFIG}/postfix-virtual.cf":/tmp/docker-mailserver/postfix-virtual.cf \
     "${IMAGE_NAME}" /bin/bash -c 'open-dkim | wc -l'
@@ -219,6 +226,7 @@ function teardown_file
 
   # check keys for localhost.localdomain
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-accounts/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/localhost.localdomain/ | wc -l'
   assert_success
@@ -232,6 +240,7 @@ function teardown_file
   # [ "${output}" -eq 0 ]
   # check presence of tables and TrustedHosts
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-accounts/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c "ls -1 /etc/opendkim | grep -E 'KeyTable|SigningTable|TrustedHosts|keys'|wc -l"
   assert_success
@@ -244,6 +253,7 @@ function teardown_file
   rm -rf "${PRIVATE_CONFIG}/without-virtual"
   mkdir -p "${PRIVATE_CONFIG}/without-virtual"
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-virtual/":/tmp/docker-mailserver/ \
     -v "${PRIVATE_CONFIG}/postfix-accounts.cf":/tmp/docker-mailserver/postfix-accounts.cf \
     "${IMAGE_NAME}" /bin/bash -c 'open-dkim | wc -l'
@@ -252,6 +262,7 @@ function teardown_file
 
   # check keys for localhost.localdomain
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-virtual/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/localhost.localdomain/ | wc -l'
   assert_success
@@ -259,6 +270,7 @@ function teardown_file
 
   # check keys for otherdomain.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-virtual/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/otherdomain.tld | wc -l'
   assert_success
@@ -266,6 +278,7 @@ function teardown_file
 
   # check presence of tables and TrustedHosts
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/without-virtual/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c "ls -1 /etc/opendkim | grep -E 'KeyTable|SigningTable|TrustedHosts|keys'|wc -l"
   assert_success
@@ -279,6 +292,7 @@ function teardown_file
 
   # generate first key
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/":/tmp/docker-mailserver/ \
     "${IMAGE_NAME}" /bin/bash -c 'open-dkim keysize 2048 domain domain1.tld | wc -l'
   assert_success
@@ -286,6 +300,7 @@ function teardown_file
 
   # generate two additional keys different to the previous one
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/":/tmp/docker-mailserver/ \
     "${IMAGE_NAME}" /bin/bash -c 'open-dkim keysize 2048 domain "domain2.tld,domain3.tld" | wc -l'
   assert_success
@@ -293,6 +308,7 @@ function teardown_file
 
   # generate an additional key whilst providing already existing domains
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/":/tmp/docker-mailserver/ \
     "${IMAGE_NAME}" /bin/bash -c 'open-dkim keysize 2048 domain "domain3.tld,domain4.tld" | wc -l'
   assert_success
@@ -300,6 +316,7 @@ function teardown_file
 
   # check keys for domain1.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/domain1.tld/ | wc -l'
   assert_success
@@ -307,6 +324,7 @@ function teardown_file
 
   # check keys for domain2.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/domain2.tld | wc -l'
   assert_success
@@ -314,6 +332,7 @@ function teardown_file
 
   # check keys for domain3.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/domain3.tld | wc -l'
   assert_success
@@ -321,6 +340,7 @@ function teardown_file
 
   # check keys for domain4.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c 'ls -1 /etc/opendkim/keys/domain4.tld | wc -l'
   assert_success
@@ -328,6 +348,7 @@ function teardown_file
 
   # check presence of tables and TrustedHosts
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c "ls -1 /etc/opendkim | grep -E 'KeyTable|SigningTable|TrustedHosts|keys' | wc -l"
   assert_success
@@ -335,6 +356,7 @@ function teardown_file
 
   # check valid entries actually present in KeyTable
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c \
     "egrep 'domain1.tld|domain2.tld|domain3.tld|domain4.tld' /etc/opendkim/KeyTable | wc -l"
@@ -343,6 +365,7 @@ function teardown_file
 
   # check valid entries actually present in SigningTable
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-domain/opendkim":/etc/opendkim \
     "${IMAGE_NAME}" /bin/bash -c \
     "egrep 'domain1.tld|domain2.tld|domain3.tld|domain4.tld' /etc/opendkim/SigningTable | wc -l"
@@ -357,6 +380,7 @@ function teardown_file
 
   # Generate first key
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/":/tmp/docker-mailserver/ \
     "${IMAGE_NAME:?}" /bin/sh -c "open-dkim keysize 2048 domain 'domain1.tld' selector mailer| wc -l"
   assert_success
@@ -364,6 +388,7 @@ function teardown_file
 
   # Check keys for domain1.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/opendkim":/etc/opendkim \
     "${IMAGE_NAME:?}" /bin/sh -c 'ls -1 /etc/opendkim/keys/domain1.tld/ | wc -l'
   assert_success
@@ -371,6 +396,7 @@ function teardown_file
 
   # Check key names with selector for domain1.tld
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/opendkim":/etc/opendkim \
     "${IMAGE_NAME:?}" /bin/sh -c "ls -1 /etc/opendkim/keys/domain1.tld | grep -E 'mailer.private|mailer.txt' | wc -l"
   assert_success
@@ -378,6 +404,7 @@ function teardown_file
 
   # Check presence of tables and TrustedHosts
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/opendkim":/etc/opendkim \
     "${IMAGE_NAME:?}" /bin/sh -c "ls -1 /etc/opendkim | grep -E 'KeyTable|SigningTable|TrustedHosts|keys' | wc -l"
   assert_success
@@ -385,6 +412,7 @@ function teardown_file
 
   # Check valid entries actually present in KeyTable
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/opendkim":/etc/opendkim \
     "${IMAGE_NAME:?}" /bin/sh -c \
     "grep 'domain1.tld' /etc/opendkim/KeyTable | wc -l"
@@ -393,6 +421,7 @@ function teardown_file
 
   # Check valid entries actually present in SigningTable
   run docker run --rm \
+    -e LOG_LEVEL='trace' \
     -v "${PRIVATE_CONFIG}/with-selector/opendkim":/etc/opendkim \
     "${IMAGE_NAME:?}" /bin/sh -c \
     "grep 'domain1.tld' /etc/opendkim/SigningTable | wc -l"
diff --git a/test/sedfile.bats b/test/sedfile.bats
index 35c57142..61b49ccf 100644
--- a/test/sedfile.bats
+++ b/test/sedfile.bats
@@ -18,7 +18,7 @@ function setup_file() {
 @test "checking sedfile parameter count" {
   run ${SEDFILE}
   assert_failure
-  assert_output --partial 'Error:  At least, three parameters must be given.'
+  assert_output --partial 'Error: At least three parameters must be given'
 }
 
 @test "checking sedfile substitute success" {
@@ -35,7 +35,7 @@ function setup_file() {
 @test "checking sedfile substitute failure" {
   run ${SEDFILE} -i 's|bar|baz|' "${FILE}"
   assert_failure
-  assert_output --partial "Error: sed -i s|bar|baz| /tmp/sedfile-test."
+  assert_output --partial "Error: No difference after call to 'sed' in 'sedfile' (sed -i s|bar|baz| /tmp/sedfile-test"
 
   # file unchanged?
   run test "$(< "${FILE}")" == 'foo baz'
@@ -58,7 +58,7 @@ function setup_file() {
 @test "checking sedfile substitude failure (strict)" {
   run ${SEDFILE} --strict -i 's|bar|baz|' "${FILE}"
   assert_failure
-  assert_output --partial "Error: sed -i s|bar|baz| /tmp/sedfile-test."
+  assert_output --partial "Error: No difference after call to 'sed' in 'sedfile' (sed -i s|bar|baz| /tmp/sedfile-test"
 
   # file unchanged?
   run test "$(< "${FILE}")" == 'foo baz'
diff --git a/test/tests.bats b/test/tests.bats
index 29053792..cb9c59d4 100644
--- a/test/tests.bats
+++ b/test/tests.bats
@@ -935,13 +935,13 @@ EOF
 # --- setup.sh ----------------------------------
 # -----------------------------------------------
 
-@test "setup.sh :: exit with error when no arguments provided" {
+@test "checking setup.sh: exit with error when no arguments provided" {
   run ./setup.sh
   assert_failure
   assert_line --index 0 --partial "The command '' is invalid."
 }
 
-@test "setup.sh :: exit with error when wrong arguments provided" {
+@test "checking setup.sh: exit with error when wrong arguments provided" {
   run ./setup.sh lol troll
   assert_failure
   assert_line --index 0 --partial "The command 'lol troll' is invalid."
@@ -1114,7 +1114,7 @@ EOF
   assert_failure
 }
 
-@test "setup.sh :: setup.sh config dkim help correctly displayed" {
+@test "checking setup.sh: setup.sh config dkim help correctly displayed" {
   run ./setup.sh -c mail config dkim help
   assert_success
   assert_line --index 3 --partial "    open-dkim - configure DomainKeys Identified Mail (DKIM)"