diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 2566943b..497b6f04 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -189,7 +189,7 @@ function _setup_postfix_aliases
       DOMAIN=$(echo "${FROM}" | cut -d @ -f2)
 
       # if they are equal it means the line looks like: "user1     other@domain.tld"
-      [ "${UNAME}" != "${DOMAIN}" ] && echo "${DOMAIN}" >> /tmp/vhost.tmp
+      [[ "${UNAME}" != "${DOMAIN}" ]] && echo "${DOMAIN}" >> /tmp/vhost.tmp
     done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
   else
     _notify 'inf' "Warning 'config/postfix-virtual.cf' is not provided. No mail alias/forward created."
diff --git a/Dockerfile b/Dockerfile
index 4aa97926..926c5a7b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -228,7 +228,7 @@ RUN curl -s https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem > /et
 
 COPY ./target/bin /usr/local/bin
 # Start-mailserver script
-COPY ./target/helper_functions.sh ./target/check-for-changes.sh ./target/start-mailserver.sh ./target/fail2ban-wrapper.sh ./target/postfix-wrapper.sh ./target/postsrsd-wrapper.sh ./target/docker-configomat/configomat.sh /usr/local/bin/
+COPY ./target/bin-helper.sh ./target/helper-functions.sh ./target/check-for-changes.sh ./target/start-mailserver.sh ./target/fail2ban-wrapper.sh ./target/postfix-wrapper.sh ./target/postsrsd-wrapper.sh ./target/docker-configomat/configomat.sh /usr/local/bin/
 RUN chmod +x /usr/local/bin/*
 
 # Configure supervisor
diff --git a/Makefile b/Makefile
index 6833a4bb..0defc0fb 100644
--- a/Makefile
+++ b/Makefile
@@ -19,8 +19,8 @@ build:
 backup:
 # if backup directories exist, clean hasn't been called, therefore
 # we shouldn't overwrite it. It still contains the original content.
-	@ if [ ! -d config.bak ]; then cp -rp config config.bak; fi
-	@ if [ ! -d testconfig.bak ]; then cp -rp test/config testconfig.bak; fi
+	@ if [[ ! -d config.bak ]]; then cp -rp config config.bak; fi
+	@ if [[ ! -d testconfig.bak ]]; then cp -rp test/config testconfig.bak; fi
 
 generate-accounts:
 	@ docker run --rm -e MAIL_USER=user1@localhost.localdomain -e MAIL_PASS=mypassword -t $(NAME) /bin/sh -c 'echo "$$MAIL_USER|$$(doveadm pw -s SHA512-CRYPT -u $$MAIL_USER -p $$MAIL_PASS)"' > test/config/postfix-accounts.cf
diff --git a/hooks/build b/hooks/build
index e45a55c5..93afe4d4 100755
--- a/hooks/build
+++ b/hooks/build
@@ -3,6 +3,6 @@ VCS_REF=$(git rev-parse --short HEAD)
 VCS_VERSION=$(git describe --tags --contains --always)
 
 docker build \
-	--build-arg VCS_REF="$VCS_REF" \
-	--build-arg VCS_VERSION="$VCS_VERSION" \
-	-f "$DOCKERFILE_PATH" -t "$IMAGE_NAME" .
+  --build-arg VCS_REF="$VCS_REF" \
+  --build-arg VCS_VERSION="$VCS_VERSION" \
+  -f "$DOCKERFILE_PATH" -t "$IMAGE_NAME" .
diff --git a/setup.sh b/setup.sh
index 9d8fbd1d..cf322e50 100755
--- a/setup.sh
+++ b/setup.sh
@@ -7,6 +7,7 @@ SCRIPT='SETUP'
 
 set -euEo pipefail
 trap '__log_err ${FUNCNAME[0]:-"?"} ${_:-"?"} ${LINENO:-"?"} ${?:-"?"}' ERR
+trap '_unset_vars || :' EXIT
 
 function __log_err
 {
@@ -20,14 +21,13 @@ function __log_err
     "  – function  = ${FUNC_NAME}" \
     "  – line      = ${LINE}" \
     "  – exit code = ${EXIT_CODE}"
-
-  _unset_vars
 }
 
 function _unset_vars
 {
   unset CDIR CRI INFO IMAGE_NAME CONTAINER_NAME DEFAULT_CONFIG_PATH
   unset USE_CONTAINER WISHED_CONFIG_PATH CONFIG_PATH VOLUME USE_TTY
+  unset SCRIPT
 }
 
 function _get_current_directory
@@ -340,16 +340,13 @@ function _main
             _docker_container /bin/bash -c "${@}"
           fi
           ;;
-        *        ) _usage ; _unset_vars ; exit 1 ;;
+        *        ) _usage ; exit 1 ;;
       esac
       ;;
 
-    help) _usage ;;
-
-    *            ) _usage ; _unset_vars ; exit 1 ;;
+    help ) _usage ;;
+    *    ) _usage ; exit 1 ;;
   esac
-
-  _unset_vars
 }
 
 _main "${@}"
diff --git a/target/bin-helper.sh b/target/bin-helper.sh
new file mode 100755
index 00000000..169dc510
--- /dev/null
+++ b/target/bin-helper.sh
@@ -0,0 +1,16 @@
+#! /bin/bash
+
+# version   0.1.0
+# executed  from scripts in target/bin/
+# task      provides frequently used functions
+
+function errex
+{
+  echo "${@}" 1>&2
+  exit 1
+}
+
+function escape
+{
+  echo "${1//./\\.}"
+}
diff --git a/target/bin/addalias b/target/bin/addalias
index bec227b5..f8cbcd56 100755
--- a/target/bin/addalias
+++ b/target/bin/addalias
@@ -1,31 +1,25 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-virtual.cf}
 
-EMAIL="$1"
-RECIPIENT="$2"
+EMAIL="${1}"
+RECIPIENT="${2}"
 
-usage() {
-	echo "Usage: addalias <alias@domain> <recipient@other>"
-}
+function usage  { echo "Usage: addalias <alias@domain> <recipient@other>" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${EMAIL} ]] && { usage ; errex "Error: No alias specified" ; }
+[[ -z ${RECIPIENT} ]] && { usage ; errex "Error: No recipient specified" ; }
 
-escape() {
-	echo "${1//./\\.}"
-}
+grep \
+  -qi "^$(escape "${EMAIL}")[a-zA-Z@.\ ]*$(escape "${RECIPIENT}")" \
+  "${DATABASE}" 2>/dev/null && errex "Alias \"${EMAIL} ${RECIPIENT}\" already exists"
 
-[ -z "$EMAIL" ] && { usage; errex "Error: No alias specified"; }
-[ -z "$RECIPIENT" ] && { usage; errex "Error: No recipient specified"; }
-
-grep -qi "^$(escape $EMAIL)[a-zA-Z@.\ ]*$(escape $RECIPIENT)" $DATABASE 2>/dev/null &&
-	errex "Alias \"$EMAIL $RECIPIENT\" already exists"
-
-if grep -qi "^$(escape $EMAIL)" $DATABASE 2>/dev/null; then
-        sed -i "/$EMAIL/s/$/,$RECIPIENT/" $DATABASE
-    else
-        echo "$EMAIL $RECIPIENT" >> $DATABASE
+if grep -qi "^$(escape "${EMAIL}")" "${DATABASE}" 2>/dev/null
+then
+  sed -i "/${EMAIL}/s/$/,${RECIPIENT}/" "${DATABASE}"
+else
+  echo "${EMAIL} ${RECIPIENT}" >> "${DATABASE}"
 fi
diff --git a/target/bin/addmailuser b/target/bin/addmailuser
index bf9fe61e..8eeb1263 100755
--- a/target/bin/addmailuser
+++ b/target/bin/addmailuser
@@ -1,41 +1,36 @@
 #! /bin/bash
 
+# shellcheck disable=SC2094
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-USER="$1"
+USER="${1}"
 shift
-PASSWD="$@"
+PASSWD="${*}"
 
-usage() {
-	echo "Usage: addmailuser <user@domain> [<password>]"
-}
+function usage  { echo "Usage: addmailuser <user@domain> [<password>]" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
-
-escape() {
-	echo "${1//./\\.}"
-}
-
-[ -z "$USER" ] && { usage; errex "no username specified"; }
-expr index "$USER" "@" >/dev/null || { usage; errex "username must include the domain"; }
+[[ -z ${USER} ]] && { usage ; errex "no username specified" ; }
+[[ "${USER}" =~ .*\@.* ]] || { usage ; errex "username must include the domain" ; }
 
 # Protect config file with lock to avoid race conditions
-touch $DATABASE
+touch "${DATABASE}"
 (
   flock -e 200
 
-  grep -qi "^$(escape "$USER")|" $DATABASE 2>/dev/null &&
-    errex "User \"$USER\" already exists"
+  grep -qi "^$(escape "${USER}")|" "${DATABASE}" 2>/dev/null &&
+    errex "User \"${USER}\" already exists"
 
-  if [ -z "$PASSWD" ]; then
-    read -s -p "Enter Password: " PASSWD
+  if [[ -z ${PASSWD} ]]
+  then
+    read -r -s -p "Enter Password: " PASSWD
     echo
-    [ -z "$PASSWD" ] && errex "Password must not be empty"
+    [[ -z ${PASSWD} ]] && errex "Password must not be empty"
   fi
 
-  HASH="$(doveadm pw -s SHA512-CRYPT -u "$USER" -p "$PASSWD")"
-  echo "$USER|$HASH" >> $DATABASE
-) 200<$DATABASE
+  HASH="$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")"
+  echo "${USER}|${HASH}" >> "${DATABASE}"
+) 200< "${DATABASE}"
diff --git a/target/bin/addrelayhost b/target/bin/addrelayhost
index ea5e5ce0..1b8ca15d 100755
--- a/target/bin/addrelayhost
+++ b/target/bin/addrelayhost
@@ -1,33 +1,26 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-relaymap.cf}
 
-DOMAIN="$1"
-HOST="$2"
-PORT="$3"
+DOMAIN="${1}"
+HOST="${2}"
+PORT="${3}"
 
-usage() {
-	echo "Usage: addrelayhost <domain> <host> [<port>]"
-}
+function usage  { echo "Usage: addrelayhost <domain> <host> [<port>]" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${DOMAIN} ]] && { usage ; errex "no domain specified" ; }
+[[ -z ${HOST} ]] && { usage ; errex "no relay host specified" ; }
 
-escape() {
-	echo "${1//./\\.}"
-}
+[[ -z ${PORT} ]] && PORT=25
 
-[ -z "$DOMAIN" ] && { usage; errex "no domain specified"; }
-[ -z "$HOST" ] && { usage; errex "no relay host specified"; }
-
-if [ -z "$PORT" ]; then
-	PORT=25
-fi
-
-if grep -qi "^@$DOMAIN" $DATABASE 2>/dev/null; then
-	sed -i "s ^@"$DOMAIN".* "@$DOMAIN"\t\t["$HOST"]:"$PORT" " $DATABASE
+if grep -qi "^@${DOMAIN}" "${DATABASE}" 2>/dev/null
+then
+  # TODO check if fixed
+  # sed -i "s ^@${DOMAIN}.* @${DOMAIN}\t\t[${HOST}]:${PORT}" "${DATABASE}"
+  sed -i "s ^@""${DOMAIN}"".* ""@""${DOMAIN}""\t\t[""${HOST}""]:""${PORT}"" " "${DATABASE}"
 else
-	echo -e "@$DOMAIN\t\t[$HOST]:$PORT" >> $DATABASE
+  echo -e "@${DOMAIN}\t\t[${HOST}]:${PORT}" >> "${DATABASE}"
 fi
diff --git a/target/bin/addsaslpassword b/target/bin/addsaslpassword
index ac372267..780e74a5 100755
--- a/target/bin/addsaslpassword
+++ b/target/bin/addsaslpassword
@@ -1,35 +1,29 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-sasl-password.cf}
 
-DOMAIN="$1"
-USER="$2"
-PASSWD="$3"
+DOMAIN="${1}"
+USER="${2}"
+PASSWD="${3}"
 
-usage() {
-	echo "Usage: addsaslpassword <domain> <username> <password>"
-}
+function usage  { echo "Usage: addsaslpassword <domain> <username> <password>" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${DOMAIN} ]] && { usage ; errex "no domain specified" ; }
+[[ -z ${USER} ]] && { usage ; errex "no username specified" ; }
 
-escape() {
-	echo "${1//./\\.}"
-}
-
-[ -z "$DOMAIN" ] && { usage; errex "no domain specified"; }
-[ -z "$USER" ] && { usage; errex "no username specified"; }
-
-if [ -z "$PASSWD" ]; then
-	read -s -p "Enter Password: " PASSWD
-	echo
-	[ -z "$PASSWD" ] && errex "Password must not be empty"
+if [[ -z ${PASSWD} ]]
+then
+  read -r -s -p "Enter Password: " PASSWD
+  echo
+  [[ -z ${PASSWD} ]] && errex "Password must not be empty"
 fi
 
-if grep -qi "^@$DOMAIN" $DATABASE 2>/dev/null; then
-	sed -i "s ^@"$DOMAIN".* "@$DOMAIN"\t\t"$USER":"$PASSWD" " $DATABASE
+if grep -qi "^@${DOMAIN}" "${DATABASE}" 2>/dev/null
+then
+  sed -i "s ^@""${DOMAIN}"".* ""@""${DOMAIN}""\t\t""${USER}"":""${PASSWD}"" " "${DATABASE}"
 else
-	echo -e "@$DOMAIN\t\t$USER:$PASSWD" >> $DATABASE
+  echo -e "@${DOMAIN}\t\t${USER}:${PASSWD}" >> "${DATABASE}"
 fi
diff --git a/target/bin/debug-fetchmail b/target/bin/debug-fetchmail
index d2c21ce6..d5ff3ffb 100755
--- a/target/bin/debug-fetchmail
+++ b/target/bin/debug-fetchmail
@@ -1,11 +1,11 @@
-#! /bin/sh
+#! /bin/bash
 
 /usr/local/bin/setup-fetchmail
 
 su -s /bin/sh -c "/usr/bin/fetchmail \
-	--verbose \
-	--daemon 0 \
-	--check \
-	--nosyslog \
-	--nodetach \
-	-f /etc/fetchmailrc" fetchmail <&- 2>&1
+  --verbose \
+  --daemon 0 \
+  --check \
+  --nosyslog \
+  --nodetach \
+  -f /etc/fetchmailrc" fetchmail <&- 2>&1
diff --git a/target/bin/delalias b/target/bin/delalias
index 07faed9a..9077c251 100755
--- a/target/bin/delalias
+++ b/target/bin/delalias
@@ -1,29 +1,19 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-virtual.cf}
 
-EMAIL="$1"
-RECIPIENT="$2"
+EMAIL="${1}"
+RECIPIENT="${2}"
 
-usage() {
-	echo "Usage: delalias <alias@domain> <recipient@other>"
-}
+function usage  { echo "Usage: delalias <alias@domain> <recipient@other>" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${EMAIL} ]] && { usage ; errex "Error: No alias specified" ; }
+[[ -z ${RECIPIENT} ]] && { usage ; errex "Error: No recipient specified" ; }
+[[ -s ${DATABASE} ]] || exit 0
 
-escape() {
-	echo "${1//./\\.}"
-}
-
-[ -z "$EMAIL" ] && { usage; errex "Error: No alias specified"; }
-[ -z "$RECIPIENT" ] && { usage; errex "Error: No recipient specified"; }
-
-[ -s "$DATABASE" ] || exit 0
-
-#CNT=$(grep "^$EMAIL" $DATABASE | wc -w | awk '{print $1}')
-sed -i -e "/^$EMAIL *$RECIPIENT$/d" \
-       -e "/^$EMAIL/s/,$RECIPIENT//g" \
-       -e "/^$EMAIL/s/$RECIPIENT,//g" $DATABASE
+sed -i -e "/^${EMAIL} *${RECIPIENT}$/d" \
+  -e "/^${EMAIL}/s/,${RECIPIENT}//g" \
+  -e "/^${EMAIL}/s/${RECIPIENT},//g" "${DATABASE}"
diff --git a/target/bin/delmailuser b/target/bin/delmailuser
index 65198e69..e2a1dd37 100755
--- a/target/bin/delmailuser
+++ b/target/bin/delmailuser
@@ -1,69 +1,93 @@
 #! /bin/bash
 
+# ? This is done to ignore the message "Make sure not to read and write
+# ? the same file in the same pipeline", which is a result of ${DATABASE}
+# ? being used below. (This disables the message file-wide.)
+# shellcheck disable=SC2094
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 ALIAS_DATABASE="/tmp/docker-mailserver/postfix-virtual.cf"
 QUOTA_DATABASE="/tmp/docker-mailserver/dovecot-quotas.cf"
 
-usage() {
-	echo "Usage: delmailuser <-y> <user@domain> <user2@anotherdomain> ..."
-	echo "	-y: don't prompt for confirmations"
+function usage
+{
+  echo "Usage: delmailuser <-y> <user@domain> <user2@anotherdomain> ..."
+  echo "	-y: don't prompt for confirmations"
 }
 
-errex() {
-	echo -e "$@" 1>&2
-	exit 1
-}
-
-escape() {
-	echo "${1//./\\.}"
-}
-
-while getopts ":y" OPT; do
-  case $OPT in
+while getopts ":y" OPT
+do
+  case ${OPT} in
     y)
       MAILDEL="y"
       ;;
-   \?)
-		 usage; errex "Invalid option: -$OPTARG"
-     ;;
+    \?)
+      usage
+      errex "Invalid option: -${OPTARG}"
+      ;;
+    *)
+      usage
+      errex "Invalid option: -${OPTARG}"
+      ;;
   esac
 done
 
 shift $((OPTIND-1))
 
-[ -z "$@" ] && { usage; errex "No user specifed"; }
-[ -s "$DATABASE" ] || exit 0
+[[ -z ${*} ]] && { usage ; errex "No user specifed" ; }
+[[ -s ${DATABASE} ]] || exit 0
 
 # Protect config file with lock to avoid race conditions
 (
   flock -e 200
 
-  for USER in "$@"; do
+  for USER in "${@}"
+  do
     # very simple plausibility check
-    [[ "$USER" != *"@"*"."* ]] && errex "No valid address: $USER"
-    MAILARR=(${USER//@/ })
-    # XXX $USER must not contain /s and other syntactic characters
-    USER=$(escape "$USER")
-    sed -i "/^"$USER"|/d" $DATABASE
-    [ $? != 0 ] && errex "$USER couldn't be deleted in $DATABASE. $?"
-    # Delete all aliases where the user is the only recipient( " $USER$" )
-    # Delete user only for all aliases that deliver to multiple recipients ( ",$USER" "$USER," )
-    sed -i -e "/ "$USER"$/d" \
-        -e "s/,"$USER"//g" \
-        -e "s/"$USER",//g" $ALIAS_DATABASE
-    [ $? = 0 ] && echo "$USER and potential aliases deleted." || errex "Aliases for $USER couldn't be deleted in $ALIAS_DATABASE. $?"
-    # remove quota directives
-    if [ -f "$QUOTA_DATABASE" ]; then
-      sed -i -e "/^$USER:.*$/d" $QUOTA_DATABASE || errex "Quota for $USER couldn't be deleted in $QUOTA_DATABASE. $?"
+    [[ ${USER} != *"@"*"."* ]] && errex "No valid address: ${USER}"
+
+    declare -a MAILARR
+    MAILARR[0]="${USER%@*}"
+    MAILARR[1]="${USER#*@}"
+
+    # XXX ${USER} must not contain /s and other syntactic characters
+    USER=$(escape "${USER}")
+
+    if ! sed -i "/^""${USER}""|/d" "${DATABASE}"
+    then
+      errex "${USER} couldn't be deleted in ${DATABASE}. ${?}"
     fi
 
-    if [ "$MAILDEL" != "y" ]; then
-      read -p "Do you want to delete the mailbox as well(all mails will be removed)?(y/n) " MAILDEL
+    # Delete all aliases where the user is the only recipient( " ${USER$}" )
+    # Delete user only for all aliases that deliver to multiple recipients ( ",${USER}" "${USER,}" )
+    if sed -i -e "/ ""${USER}""$/d" \
+        -e "s/,""${USER}""//g" \
+        -e "s/""${USER}"",//g" "${ALIAS_DATABASE}"
+    then
+      echo "${USER} and potential aliases deleted." || errex "Aliases for ${USER} couldn't be deleted in ${ALIAS_DATABASE}. ${?}"
+    fi
+
+    # remove quota directives
+    if [[ -f ${QUOTA_DATABASE} ]]
+    then
+      sed -i -e "/^${USER}:.*$/d" "${QUOTA_DATABASE}" || errex "Quota for ${USER} couldn't be deleted in ${QUOTA_DATABASE}. ${?}"
+    fi
+
+    if [[ ${MAILDEL} != "y" ]]
+    then
+      read -r -p "Do you want to delete the mailbox as well(all mails will be removed)?(y/n) " MAILDEL
       echo
     fi
-    [ "$MAILDEL" != "y" ] && errex "Leaving the mailbox untouched. If you want to delete it at a later point use \"sudo docker exec mail rm -R /var/mail/${MAILARR[1]}/${MAILARR[0]}\""
-    rm -r -f /var/mail/${MAILARR[1]}/${MAILARR[0]}
-    [ $? = 0 ] && echo "Mailbox deleted." || errex "Mailbox couldn't be deleted: $?"
+
+    [[ ${MAILDEL} != "y" ]] && errex "Leaving the mailbox untouched. If you want to delete it at a later point use \"sudo docker exec mail rm -R /var/mail/${MAILARR[1]}/${MAILARR[0]}\""
+
+    if rm -r -f "/var/mail/${MAILARR[1]}/${MAILARR[0]}"
+    then
+      echo "Mailbox deleted." || errex "Mailbox couldn't be deleted: ${?}"
+    fi
   done
 
-) 200<$DATABASE
+) 200< "${DATABASE}"
diff --git a/target/bin/delquota b/target/bin/delquota
index 737e641a..9212559e 100755
--- a/target/bin/delquota
+++ b/target/bin/delquota
@@ -1,28 +1,24 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/dovecot-quotas.cf}
 USER_DATABASE=${USER_DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-USER="$1"
+USER="${1}"
 
-usage() {
-	echo "Usage: delquota <username@domain>"
-}
+function usage  {	echo "Usage: delquota <username@domain>" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${USER} ]]  && { usage ; errex "No username specified" ; }
+[[ "${USER}" =~ .*\@.* ]] || { usage ; errex "username must include the domain"; }
 
-escape() {
-	echo "${1//./\\.}"
-}
-
-[ -z "$USER" ]  && { usage; errex "No username specified"; }
-expr index "$USER" "@" >/dev/null || { usage; errex "username must include the domain"; }
-if ! grep -qE "^$USER\|" "$USER_DATABASE"; then
-  usage; errex "user $USER does not exist"
+if ! grep -qE "^${USER}\|" "${USER_DATABASE}"
+then
+  usage
+  errex "user ${USER} does not exist"
 fi
-[ -s "$DATABASE" ] || exit 0
 
-sed -i -e "/^$USER:.*$/d" $DATABASE
+[[ -s ${DATABASE} ]] || exit 0
+
+sed -i -e "/^${USER}:.*$/d" "${DATABASE}"
diff --git a/target/bin/excluderelaydomain b/target/bin/excluderelaydomain
index 07f6dce9..b9a27a83 100755
--- a/target/bin/excluderelaydomain
+++ b/target/bin/excluderelaydomain
@@ -1,22 +1,19 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-relaymap.cf}
 
-DOMAIN="$1"
+DOMAIN="${1}"
 
-usage() {
-	echo "Usage: excluderelayhost <domain>"
-}
+function usage { echo "Usage: excluderelayhost <domain>" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${DOMAIN} ]] && { usage ; errex "no domain specified" ; }
 
-[ -z "$DOMAIN" ] && { usage; errex "no domain specified"; }
-
-if grep -qi "^@$DOMAIN" $DATABASE 2>/dev/null; then
-	sed -i "s/^@"$DOMAIN".*/@"$DOMAIN"/" $DATABASE
+if grep -qi "^@${DOMAIN}" "${DATABASE}" 2>/dev/null
+then
+  sed -i "s/^@${DOMAIN}.*/@${DOMAIN}/" "${DATABASE}"
 else
-	echo -e "@$DOMAIN" >> $DATABASE
+  echo -e "@${DOMAIN}" >> "${DATABASE}"
 fi
diff --git a/target/bin/fail2ban b/target/bin/fail2ban
old mode 100644
new mode 100755
index ceb91da8..a2854633
--- a/target/bin/fail2ban
+++ b/target/bin/fail2ban
@@ -1,46 +1,68 @@
 #! /bin/bash
 
-usage() {
-  echo "Usage: $0 [<unban> <ip-address>]"
-}
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
 
-raise() {
-  echo "$@" 1>&2
-  exit 1
-}
+function usage { echo "Usage: ${0} [<unban> <ip-address>]" ; }
 
-JAILS=$(fail2ban-client status | grep "Jail list" | cut -f2- | sed 's/,//g')
-if [ -z "$1" ]; then
+declare -a JAILS
+for LIST in $(fail2ban-client status | grep "Jail list" | cut -f2- | sed 's/,/ /g')
+do
+  JAILS+=("${LIST}")
+done
+
+if [[ -z ${1} ]]
+then
   IP_COUNT=0
-  for JAIL in $JAILS; do
-    BANNED_IP=$(iptables -L f2b-$JAIL -n | grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | grep -v '0.0.0.0')
-    if [ -n "$BANNED_IP" ]; then
-      BANNED_IP=$(echo $BANNED_IP | sed -e 's/\n/,/g')
-      echo "Banned in $JAIL: $BANNED_IP"
-      IP_COUNT=$((IP_COUNT+1))
+
+  for JAIL in "${JAILS[@]}"
+  do
+    declare -a BANNED_IPS
+
+    while read -r LINE
+    do
+      BANNED_IPS+=("$(echo "${LINE}" | grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | grep -v '0.0.0.0')")
+    done < <(iptables -L f2b-"${JAIL}" -n)
+
+    if [[ ${#BANNED_IPS[@]} -ne 0 ]]
+    then
+      for BANNED_IP in "${BANNED_IPS[@]}"
+      do
+        echo "Banned in ${JAIL}: ${BANNED_IP}"
+        IP_COUNT=$(( IP_COUNT + 1 ))
+      done
     fi
   done
-  if [ "$IP_COUNT" -eq 0 ]; then
+
+  if [[ ${IP_COUNT} -eq 0 ]]
+  then
     echo "No IPs have been banned"
   fi
 else
-  case $1 in
+  case ${1} in
     unban)
       shift
-      if [ -n "$1" ]; then
-        for JAIL in $JAILS; do
-          RESULT=`fail2ban-client set $JAIL unbanip $@`
-          if [[ "$RESULT" != *"is not banned"* ]] && [[ "$RESULT" != *"NOK"* ]]; then
-            echo -n "unbanned IP from $JAIL: "
-            echo "$RESULT"
+      if [[ -n ${1} ]]
+      then
+        for JAIL in "${JAILS[@]}"
+        do
+          RESULT="$(fail2ban-client set "${JAIL}" unbanip "${@}")"
+
+          if [[ ${RESULT} != *"is not banned"* ]] && [[ ${RESULT} != *"NOK"* ]]
+          then
+            echo -n "unbanned IP from ${JAIL}: "
+            echo "${RESULT}"
           fi
         done
       else
-        raise "You need to specify an IP address. Run \"./setup.sh debug fail2ban\" to get a list of banned IP addresses."
+        errex "You need to specify an IP address. Run \"./setup.sh debug fail2ban\" to get a list of banned IP addresses."
       fi
       ;;
+
     *)
-      usage; raise "unknown command: $1"
+      usage
+      errex "unknown command: ${1}"
       ;;
+
     esac
 fi
diff --git a/target/bin/generate-dkim-config b/target/bin/generate-dkim-config
index d27d7a55..6f37e22e 100755
--- a/target/bin/generate-dkim-config
+++ b/target/bin/generate-dkim-config
@@ -1,76 +1,89 @@
-#!/bin/sh
+#! /bin/bash
 
 touch /tmp/vhost.tmp
 
 # if no keysize is provided, 2048 is default.
-keysize=${1:-2048}
+KEYSIZE=${1:-2048}
 
-# Getting domains from mail accounts
-if [ -f /tmp/docker-mailserver/postfix-accounts.cf ]; then
-  (grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-accounts.cf || true) | while IFS=$'|' read login pass
+# Getting domains FROM mail accounts
+if [[ -f /tmp/docker-mailserver/postfix-accounts.cf ]]
+then
+  # shellcheck disable=SC2034
+  while IFS=$'|' read -r LOGIN PASS
   do
-    domain=$(echo ${login} | cut -d @ -f2)
-    echo ${domain} >> /tmp/vhost.tmp
-  done
+    DOMAIN=$(echo "${LOGIN}" | cut -d @ -f2)
+    echo "${DOMAIN}" >>/tmp/vhost.tmp
+  done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-accounts.cf || true)
 fi
 
-# Getting domains from mail aliases
-if [ -f /tmp/docker-mailserver/postfix-virtual.cf ]; then
-  (grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true) | while read from to
+# Getting domains FROM mail aliases
+if [[ -f /tmp/docker-mailserver/postfix-virtual.cf ]]
+then
+  # shellcheck disable=SC2034
+  while read -r FROM TO
   do
-    # Setting variables for better readability
-    uname=$(echo ${from} | cut -d @ -f1)
-    domain=$(echo ${from} | cut -d @ -f2)
-    # if they are equal it means the line looks like: "user1     other@domain.tld"
-    test "$uname" != "$domain" && echo ${domain} >> /tmp/vhost.tmp
-  done
+    UNAME=$(echo "${FROM}" | cut -d @ -f1)
+    DOMAIN=$(echo "${FROM}" | cut -d @ -f2)
+
+    test "${UNAME}" != "${DOMAIN}" && echo "${DOMAIN}" >>/tmp/vhost.tmp
+  done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
 fi
 
-# Keeping unique entries
-if [ -f /tmp/vhost.tmp ]; then
-  cat /tmp/vhost.tmp | sort | uniq > /tmp/vhost && rm /tmp/vhost.tmp
+# keeping unique entries
+if [[ -f /tmp/vhost.tmp ]]
+then
+  sort < /tmp/vhost.tmp | uniq >/tmp/vhost && rm /tmp/vhost.tmp
 fi
 
-# Exit if no entries found
-if [ ! -f /tmp/vhost ]; then
-	echo "No entries found, no keys to make"
-	exit 0
+# exit if no entries found
+if [[ ! -f /tmp/vhost ]]
+then
+  echo "No entries found, no keys to make"
+  exit 0
 fi
 
-grep -vE '^(\s*$|#)' /tmp/vhost | while read domainname; do
-  mkdir -p /tmp/docker-mailserver/opendkim/keys/$domainname
+while read -r DOMAINNAME
+do
+  mkdir -p "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}"
 
-  if [ ! -f "/tmp/docker-mailserver/opendkim/keys/$domainname/mail.private" ]; then
-    echo "Creating DKIM private key /tmp/docker-mailserver/opendkim/keys/$domainname/mail.private"
-    opendkim-genkey --bits=$keysize --subdomains --domain=$domainname --selector=mail -D /tmp/docker-mailserver/opendkim/keys/$domainname
+  if [[ ! -f "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}/mail.private" ]]
+  then
+    echo "Creating DKIM private key /tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}/mail.private"
+
+    opendkim-genkey --bits="${KEYSIZE}" --subdomains --DOMAIN="${DOMAINNAME}" --selector=mail -D "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}"
   fi
 
-  # Write to KeyTable if necessary
-  keytableentry="mail._domainkey.$domainname $domainname:mail:/etc/opendkim/keys/$domainname/mail.private"
-  if [ ! -f "/tmp/docker-mailserver/opendkim/KeyTable" ]; then
+  # write to KeyTable if necessary
+  KEYTABLEENTRY="mail._domainkey.${DOMAINNAME} ${DOMAINNAME}:mail:/etc/opendkim/keys/${DOMAINNAME}/mail.private"
+  if [[ ! -f "/tmp/docker-mailserver/opendkim/KeyTable" ]]
+  then
     echo "Creating DKIM KeyTable"
-    echo $keytableentry > /tmp/docker-mailserver/opendkim/KeyTable
+    echo "${KEYTABLEENTRY}" > /tmp/docker-mailserver/opendkim/KeyTable
   else
-    if ! grep -q "$keytableentry" "/tmp/docker-mailserver/opendkim/KeyTable" ; then
-        echo $keytableentry >> /tmp/docker-mailserver/opendkim/KeyTable
+    if ! grep -q "${KEYTABLEENTRY}" "/tmp/docker-mailserver/opendkim/KeyTable"
+    then
+        echo "${KEYTABLEENTRY}" >>/tmp/docker-mailserver/opendkim/KeyTable
     fi
   fi
 
-  # Write to SigningTable if necessary
-  signingtableentry="*@$domainname mail._domainkey.$domainname"
-  if [ ! -f "/tmp/docker-mailserver/opendkim/SigningTable" ]; then
+  # write to SigningTable if necessary
+  SIGNINGTABLEENTRY="*@${DOMAINNAME} mail._domainkey.${DOMAINNAME}"
+  if [[ ! -f /tmp/docker-mailserver/opendkim/SigningTable ]]
+  then
     echo "Creating DKIM SigningTable"
-    echo "*@$domainname mail._domainkey.$domainname" > /tmp/docker-mailserver/opendkim/SigningTable
+    echo "*@${DOMAINNAME} mail._domainkey.${DOMAINNAME}" >/tmp/docker-mailserver/opendkim/SigningTable
   else
-    if ! grep -q "$signingtableentry" "/tmp/docker-mailserver/opendkim/SigningTable" ; then
-      echo $signingtableentry >> /tmp/docker-mailserver/opendkim/SigningTable
+    if ! grep -q "${SIGNINGTABLEENTRY}" /tmp/docker-mailserver/opendkim/SigningTable
+    then
+      echo "${SIGNINGTABLEENTRY}" >> /tmp/docker-mailserver/opendkim/SigningTable
     fi
   fi
-done
+done < <(grep -vE '^(\s*$|#)' /tmp/vhost)
 
-# Creates TrustedHosts if missing
-if [ -d "/tmp/docker-mailserver/opendkim" ] && [ ! -f "/tmp/docker-mailserver/opendkim/TrustedHosts" ]; then
-  echo "Creating DKIM TrustedHosts";
-  echo "127.0.0.1" > /tmp/docker-mailserver/opendkim/TrustedHosts
-  echo "localhost" >> /tmp/docker-mailserver/opendkim/TrustedHosts
+# creates TrustedHosts if missing
+if [[ -d /tmp/docker-mailserver/opendkim ]] && [[ ! -f /tmp/docker-mailserver/opendkim/TrustedHosts ]]
+then
+  echo "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/generate-dkim-domain b/target/bin/generate-dkim-domain
old mode 100644
new mode 100755
index 587b0f94..4712892b
--- a/target/bin/generate-dkim-domain
+++ b/target/bin/generate-dkim-domain
@@ -1,39 +1,44 @@
-#!/bin/sh
+#! /bin/bash
 
 set -e
 
-if [ $# -ne 1 ]; then
-    echo $0: "usage: generate-dkim-domain domain"
-    exit 1
+if [[ ${#} -ne 1 ]]
+then
+  echo "${0}: usage: generate-dkim-domain domain"
+  exit 1
 fi
 
-domainname=$1
+DOMAINNAME=${1}
+mkdir -p "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}"
 
-mkdir -p /tmp/docker-mailserver/opendkim/keys/$domainname
-
-if [ ! -f "/tmp/docker-mailserver/opendkim/keys/$domainname/mail.private" ]; then
-    echo "Creating DKIM private key /tmp/docker-mailserver/opendkim/keys/$domainname/mail.private"
-    opendkim-genkey --subdomains --domain=$domainname --selector=mail -D /tmp/docker-mailserver/opendkim/keys/$domainname
+if [[ ! -f "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}/mail.private" ]]
+then
+  echo "Creating DKIM private key /tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}/mail.private"
+  opendkim-genkey --subdomains --domain="${DOMAINNAME}" --selector=mail -D "/tmp/docker-mailserver/opendkim/keys/${DOMAINNAME}"
 fi
 
 # Write to KeyTable if necessary
-keytableentry="mail._domainkey.$domainname $domainname:mail:/etc/opendkim/keys/$domainname/mail.private"
-if [ ! -f "/tmp/docker-mailserver/opendkim/KeyTable" ]; then
-    echo "Creating DKIM KeyTable"
-    echo $keytableentry > /tmp/docker-mailserver/opendkim/KeyTable
+KEYTABLEENTRY="mail._domainkey.${DOMAINNAME} ${DOMAINNAME}:mail:/etc/opendkim/keys/${DOMAINNAME}/mail.private"
+if [[ ! -f "/tmp/docker-mailserver/opendkim/KeyTable" ]]
+then
+  echo "Creating DKIM KeyTable"
+  echo "${KEYTABLEENTRY}" > /tmp/docker-mailserver/opendkim/KeyTable
 else
-    if ! grep -q "$keytableentry" "/tmp/docker-mailserver/opendkim/KeyTable" ; then
-        echo $keytableentry >> /tmp/docker-mailserver/opendkim/KeyTable
-    fi
+  if ! grep -q "${KEYTABLEENTRY}" "/tmp/docker-mailserver/opendkim/KeyTable"
+  then
+    echo "${KEYTABLEENTRY}" >> /tmp/docker-mailserver/opendkim/KeyTable
+  fi
 fi
 
 # Write to SigningTable if necessary
-signingtableentry="*@$domainname mail._domainkey.$domainname"
-if [ ! -f "/tmp/docker-mailserver/opendkim/SigningTable" ]; then
-    echo "Creating DKIM SigningTable"
-    echo "*@$domainname mail._domainkey.$domainname" > /tmp/docker-mailserver/opendkim/SigningTable
+SIGNINGTABLEENTRY="*@${DOMAINNAME} mail._domainkey.${DOMAINNAME}"
+if [[ ! -f /tmp/docker-mailserver/opendkim/SigningTable ]]
+then
+  echo "Creating DKIM SigningTable"
+  echo "*@${DOMAINNAME} mail._domainkey.${DOMAINNAME}" > /tmp/docker-mailserver/opendkim/SigningTable
 else
-    if ! grep -q "$signingtableentry" "/tmp/docker-mailserver/opendkim/SigningTable" ; then
-        echo $signingtableentry >> /tmp/docker-mailserver/opendkim/SigningTable
-    fi
+  if ! grep -q "${SIGNINGTABLEENTRY}" "/tmp/docker-mailserver/opendkim/SigningTable"
+  then
+    echo "${SIGNINGTABLEENTRY}" >>/tmp/docker-mailserver/opendkim/SigningTable
+  fi
 fi
diff --git a/target/bin/generate-ssl-certificate b/target/bin/generate-ssl-certificate
index aaf00fcc..00de8b30 100755
--- a/target/bin/generate-ssl-certificate
+++ b/target/bin/generate-ssl-certificate
@@ -1,26 +1,32 @@
-#!/bin/bash
+#! /bin/bash
 
 set -e
 
 # check if FQDN was passed as arguement in setup.sh
-if [ -z "$1" ]; then
-	FQDN="$(hostname --fqdn)"
+if [[ -z ${1} ]]
+then
+  FQDN="$(hostname --fqdn)"
 else
-	FQDN="$1"
+  FQDN="${1}"
 fi
 
-ssl_cfg_path="/tmp/docker-mailserver/ssl"
+SSL_CFG_PATH="/tmp/docker-mailserver/ssl"
 
-if [ ! -d "$ssl_cfg_path" ]; then
-	mkdir "$ssl_cfg_path"
+if [[ ! -d ${SSL_CFG_PATH} ]]
+then
+  mkdir "${SSL_CFG_PATH}"
 fi
 
-cd "$ssl_cfg_path" || { echo "cd $ssl_cfg_path error"; exit; }
+cd "${SSL_CFG_PATH}" || { echo "cd ${SSL_CFG_PATH} error" ; exit ; }
+
 # Create CA certificate
 /usr/lib/ssl/misc/CA.pl -newca
+
 # Create an unpassworded private key and create an unsigned public key certificate
-openssl req -new -nodes -keyout "$ssl_cfg_path"/"$FQDN"-key.pem -out "$ssl_cfg_path"/"$FQDN"-req.pem -days 3652
+openssl req -new -nodes -keyout "${SSL_CFG_PATH}"/"${FQDN}"-key.pem -out "${SSL_CFG_PATH}"/"${FQDN}"-req.pem -days 3652
+
 # Sign the public key certificate with CA certificate
-openssl ca -out "$ssl_cfg_path"/"$FQDN"-cert.pem -infiles "$ssl_cfg_path"/"$FQDN"-req.pem
+openssl ca -out "${SSL_CFG_PATH}"/"${FQDN}"-cert.pem -infiles "${SSL_CFG_PATH}"/"${FQDN}"-req.pem
+
 # Combine certificates for courier
-cat "$ssl_cfg_path"/"$FQDN"-key.pem "$ssl_cfg_path"/"$FQDN"-cert.pem > "$ssl_cfg_path"/"$FQDN"-combined.pem
+cat "${SSL_CFG_PATH}"/"${FQDN}"-key.pem "${SSL_CFG_PATH}"/"${FQDN}"-cert.pem > "${SSL_CFG_PATH}"/"${FQDN}"-combined.pem
diff --git a/target/bin/listalias b/target/bin/listalias
index f6848ec5..d93d4380 100755
--- a/target/bin/listalias
+++ b/target/bin/listalias
@@ -1,13 +1,11 @@
 #! /bin/bash
 
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-virtual.cf}
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -f ${DATABASE} ]] || errex "Error: No postfix-virtual.cf file"
+[[ -s ${DATABASE} ]] || errex "Error: Empty postfix-virtual.cf - no aliases have been added"
 
-[ -f $DATABASE ] || errex "Error: No postfix-virtual.cf file"
-[ -s $DATABASE ] || errex "Error: Empty postfix-virtual.cf - no aliases have been added"
-
-(grep -v "^\s*$\|^\s*\#" $DATABASE || true)
+( grep -v "^\s*$\|^\s*\#" "${DATABASE}" || true )
diff --git a/target/bin/listmailuser b/target/bin/listmailuser
index be6a4935..c92aff83 100755
--- a/target/bin/listmailuser
+++ b/target/bin/listmailuser
@@ -1,18 +1,20 @@
 #! /bin/bash
 
+# ? This is done to ignore the message "Make sure not to read and write
+# ? the same file in the same pipeline", which is a result of ${DATABASE}
+# ? being used below. (This disables the message file-wide.)
+# shellcheck disable=SC2094
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
-
-[ -f $DATABASE ] || errex "No postfix-accounts.cf file"
-[ -s $DATABASE ] || errex "Empty postfix-accounts.cf - no users have been added"
+[[ -f ${DATABASE} ]] || errex "Error: No postfix-virtual.cf file"
+[[ -s ${DATABASE} ]] || errex "Error: Empty postfix-virtual.cf - no aliases have been added"
 
 # Lock database even though we are only reading
 (
   flock -e 200
-  (grep -v "^\s*$\|^\s*\#" "$DATABASE" || true) | awk -F '|' '{ print $1; }'
-) 200<$DATABASE
-
+  ( grep -v "^\s*$\|^\s*\#" "${DATABASE}" || true ) | awk -F '|' '{ print $1; }'
+) 200< "${DATABASE}"
diff --git a/target/bin/postfix-summary b/target/bin/postfix-summary
index db3138bf..cb94d492 100755
--- a/target/bin/postfix-summary
+++ b/target/bin/postfix-summary
@@ -1,17 +1,19 @@
-#!/bin/bash
+#! /bin/bash
 
-HOSTNAME=$1
-RECIPIENT=$2
-SENDER=$3
-errex() {
-  echo -e "$@" 1>&2
-  exit 1
-}
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
 
-test -x /usr/sbin/pflogsumm || errex "Critical: /usr/sbin/pflogsumm not found"
+HOSTNAME=${1}
+RECIPIENT=${2}
+SENDER=${3}
 
-# The case that the mail.log.1 file isn't readable shouldn't actually be possible with logrotate not rotating empty files.. But you never know!
-if [ -r "/var/log/mail/mail.log.1" ]; then
+[[ -x /usr/sbin/pflogsumm ]] || errex "Critical: /usr/sbin/pflogsumm not found"
+
+# The case that the mail.log.1 file isn't readable shouldn't
+# actually be possible with logrotate not rotating empty files..
+# But you never know!
+if [[ -r "/var/log/mail/mail.log.1" ]]
+then
   BODY=$(/usr/sbin/pflogsumm /var/log/mail/mail.log.1 --problems-first)
 else
   BODY="Error: Mail log not readable or not found: /var/log/mail/mail.log.1
@@ -19,15 +21,15 @@ else
 In case of mail inactivity since the last report, this might be considered a nuisance warning.
 
 Yours faithfully,
-The $HOSTNAME Mailserver"
+The ${HOSTNAME} Mailserver"
 fi
 
 sendmail -t <<EOF
-From: $SENDER
-To: $RECIPIENT
-Subject: Postfix Summary for $HOSTNAME
+From: ${SENDER}
+To: ${RECIPIENT}
+Subject: Postfix Summary for ${HOSTNAME}
 Content-Transfer-Encoding: 8bit
 Content-Type: text/plain; charset=UTF-8
 
-$BODY
+${BODY}
 EOF
diff --git a/target/bin/report-pflogsumm-yesterday b/target/bin/report-pflogsumm-yesterday
index 6af20d10..beed6458 100755
--- a/target/bin/report-pflogsumm-yesterday
+++ b/target/bin/report-pflogsumm-yesterday
@@ -1,27 +1,27 @@
-#!/bin/bash
+#! /bin/bash
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 set -o errexit
 set -o pipefail
 set -o nounset
 
-HOSTNAME=$1
-RECIPIENT=$2
-SENDER=$3
-errex() {
-  echo -e "$@" 1>&2
-  exit 1
-}
+HOSTNAME=${1}
+RECIPIENT=${2}
+SENDER=${3}
 
-test -x /usr/sbin/pflogsumm || errex "Critical: /usr/sbin/pflogsumm not found"
+[[ -x /usr/sbin/pflogsumm ]] || errex "Critical: /usr/sbin/pflogsumm not found"
 
+# shellcheck disable=SC2046
 BODY=$(gzip -cdfq $(ls -tr /var/log/mail/mail.log*) | /usr/sbin/pflogsumm --problems_first -d yesterday)
 
 sendmail -t <<EOF
-From: $SENDER
-To: $RECIPIENT
-Subject: Postfix summary for $HOSTNAME sent $(date '+%Y-%m-%d_%H%M%S')
+From: ${SENDER}
+To: ${RECIPIENT}
+Subject: Postfix summary for ${HOSTNAME} sent $(date '+%Y-%m-%d_%H%M%S')
 Content-Transfer-Encoding: 8bit
 Content-Type: text/plain; charset=UTF-8
 
-$BODY
+${BODY}
 EOF
-
diff --git a/target/bin/restrict-access b/target/bin/restrict-access
index aaa46ddc..29d1275f 100755
--- a/target/bin/restrict-access
+++ b/target/bin/restrict-access
@@ -1,64 +1,62 @@
 #! /bin/bash
 
-MODE="$1"
-USER="$3"
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
 
-usage() {
-	echo "Usage: $0 <add|del|list> <send|receive> [<email@domain.com>]"
-}
+MODE="${1}"
+USER="${3}"
 
-raise() {
-	echo "$@" 1>&2
-	exit 1
-}
+function usage  {	echo "Usage: ${0} <add|del|list> <send|receive> [<email@domain.com>]" ; }
 
-escape() {
-	echo "${1//./\\.}"
-}
-[ -z "$MODE" ] && raise "missing parameters: <add|del|list> <send|receive> [<email@domain.com>]"
+[[ -z ${MODE} ]] && errex "missing parameters: <add|del|list> <send|receive> [<email@domain.com>]"
 
-case $2 in
-	send)
-		DATABASE="/tmp/docker-mailserver/postfix-send-access.cf"
-		;;
-	receive)
-		DATABASE="/tmp/docker-mailserver/postfix-receive-access.cf"
-		;;
-	*)
-		usage; raise "missing parameters. Specify \"send\" or \"receive\"";
-		;;
+case ${2} in
+  send)
+    DATABASE="/tmp/docker-mailserver/postfix-send-access.cf"
+    ;;
+  receive)
+    DATABASE="/tmp/docker-mailserver/postfix-receive-access.cf"
+    ;;
+  *)
+    usage
+    errex "missing parameters. Specify \"send\" or \"receive\""
+    ;;
 esac
 
-if [ -z "$USER" ] && [ "$MODE" != list ]; then
-	read -p "User(user@domain.com): " USER
-	echo
-	[ -z "$USER" ] && raise "User must not be empty"
+if [[ -z ${USER} ]] && [[ ${MODE} != list ]]
+then
+  read -r -p "User(user@domain.com): " USER
+  echo
+  [[ -z ${USER} ]] && errex "User must not be empty"
 fi
 
+case ${MODE} in
+  add)
+    grep -qi "^$(escape "${USER}")" "${DATABASE}" 2>/dev/null && errex "User \"${USER}\" already denied to ${2} mails"
 
+    if [[ ! -f ${DATABASE} ]]
+    then
+      # shellcheck disable=SC2015
+      [[ ${DATABASE} = *"send"* ]] && \
+          sed -i 's|smtpd_sender_restrictions =|smtpd_sender_restrictions = check_sender_access texthash:/tmp/docker-mailserver/postfix-send-access.cf,|' /etc/postfix/main.cf \
+        || sed -i 's|smtpd_recipient_restrictions =|smtpd_recipient_restrictions = check_recipient_access texthash:/tmp/docker-mailserver/postfix-receive-access.cf,|' /etc/postfix/main.cf
 
-case $MODE in
-	add)
-		grep -qi "^$(escape "$USER")" $DATABASE 2>/dev/null &&
-			raise "User \"$USER\" already denied to $2 mails"
-		if [ ! -f $DATABASE ]; then
-			[[ $DATABASE = *"send"* ]] && \
-					sed -i 's|smtpd_sender_restrictions =|smtpd_sender_restrictions = check_sender_access texthash:/tmp/docker-mailserver/postfix-send-access.cf,|' /etc/postfix/main.cf \
-				|| sed -i 's|smtpd_recipient_restrictions =|smtpd_recipient_restrictions = check_recipient_access texthash:/tmp/docker-mailserver/postfix-receive-access.cf,|'  /etc/postfix/main.cf
-			service postfix reload > /dev/null
-		fi
-		echo -e "$USER \t\t REJECT" >>$DATABASE
-	;;
-	del)
-		sed -ie "/^$(escape "$USER")/d" $DATABASE 2>/dev/null ||
-			raise "User \"$USER\" not found."
-	;;
-	list)
-		grep "REJECT" $DATABASE 2>/dev/null ||
-		    echo "Everyone is allowed to $2 mails."
+      service postfix reload >/dev/null
+    fi
+
+    echo -e "${USER} \t\t REJECT" >>"${DATABASE}"
+  ;;
+
+  del)
+    sed -ie "/^$(escape "${USER}")/d" "${DATABASE}" 2>/dev/null || errex "User \"${USER}\" not found."
+  ;;
+
+  list)
+    grep "REJECT" "${DATABASE}" 2>/dev/null || echo "Everyone is allowed to ${2} mails."
     ;;
-	*)
-		usage; raise "missing mode. Specify \"add\", \"del\" or \"list\"";
-	;;
-esac
+  *)
+    usage
+    errex "missing mode. Specify \"add\", \"del\" or \"list\""
+  ;;
 
+esac
diff --git a/target/bin/setquota b/target/bin/setquota
index 48c6f18e..ed2cfad9 100755
--- a/target/bin/setquota
+++ b/target/bin/setquota
@@ -1,49 +1,56 @@
 #! /bin/bash
 
+# ? This is done to ignore the message "Make sure not to read and write
+# ? the same file in the same pipeline", which is a result of ${DATABASE}
+# ? being used below. (This disables the message file-wide.)
+# shellcheck disable=SC2094
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/dovecot-quotas.cf}
 USER_DATABASE=${USER_DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-USER="$1"
+USER="${1}"
 shift
-QUOTA="$@"
+QUOTA="${*}"
 
-usage() {
-	echo "Usage: setquota <user@domain> [<quota>]"
-}
+function usage  { echo "Usage: setquota <user@domain> [<quota>]" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${USER} ]] && { usage ; errex "no username specified" ; }
+[[ "${USER}" =~ .*\@.* ]] || { usage ; errex "username must include the domain" ; }
 
-[ -z "$USER" ] && { usage; errex "no username specified"; }
-expr index "$USER" "@" >/dev/null || { usage; errex "username must include the domain"; }
-if ! grep -qE "^$USER\|" "$USER_DATABASE"; then
-  usage; errex "user $USER does not exist"
+if ! grep -qE "^${USER}\|" "${USER_DATABASE}"
+then
+  usage; errex "user ${USER} does not exist"
 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))"
+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
 
 # Protect config file with lock to avoid race conditions
-touch $DATABASE
+touch "${DATABASE}"
 (
   flock -e 200
 
-  if [ -z "$QUOTA" ]; then
-    read -s "Enter quota (e.g. 10M): " QUOTA
+  if [ -z "${QUOTA}" ]; then
+    read -r -s "Enter quota (e.g. 10M): " QUOTA
     echo
-    [ -z "$QUOTA" ] && errex "Quota must not be empty. Use 0 for unlimited quota"
+    [[ -z "${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))"
+  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
+  delquota "${USER}"
+  echo "${USER}:${QUOTA}" >>"${DATABASE}"
+) 200< "${DATABASE}"
 
diff --git a/target/bin/setup-fetchmail b/target/bin/setup-fetchmail
index 79e04a95..7f0897a1 100755
--- a/target/bin/setup-fetchmail
+++ b/target/bin/setup-fetchmail
@@ -1,13 +1,14 @@
-#! /bin/sh
+#! /bin/bash
 
 CONF=/tmp/docker-mailserver/fetchmail.cf
 RC=/etc/fetchmailrc
 
-if [ -f "$CONF" ]; then
-	cat /etc/fetchmailrc_general $CONF > $RC
+if [[ -f ${CONF} ]]
+then
+  cat /etc/fetchmailrc_general "${CONF}" >"${RC}"
 else
-	cat /etc/fetchmailrc_general > $RC
+  cat /etc/fetchmailrc_general >"${RC}"
 fi
 
-chmod 700 $RC
-chown fetchmail:root $RC
+chmod 700 "${RC}"
+chown fetchmail:root "${RC}"
diff --git a/target/bin/updatemailuser b/target/bin/updatemailuser
index cf9a4a8c..61ab0c34 100755
--- a/target/bin/updatemailuser
+++ b/target/bin/updatemailuser
@@ -1,39 +1,35 @@
 #! /bin/bash
 
+# ? This is done to ignore the message "Make sure not to read and write
+# ? the same file in the same pipeline", which is a result of ${DATABASE}
+# ? being used below. (This disables the message file-wide.)
+# shellcheck disable=SC2094
+
+# shellcheck source=../bin-helper.sh
+. /usr/local/bin/bin-helper.sh
+
 DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}
 
-USER="$1"
+USER="${1}"
 shift
-PASSWD="$@"
+PASSWD="${*}"
 
-usage() {
-	echo "Usage: updatemailuser <user@domain.tld> [password]"
-}
+function usage  {	echo "Usage: updatemailuser <user@domain.tld> [password]" ; }
 
-errex() {
-	echo "$@" 1>&2
-	exit 1
-}
+[[ -z ${USER} ]] && { usage ; errex "no username specified" ; }
 
-escape() {
-	echo "${1//./\\.}"
-}
-
-[ -z "$USER" ] && { usage; errex "no username specified"; }
-
-if [ -z "$PASSWD" ]; then
-	read -s -p "Enter Password: " PASSWD
-	echo
-	[ -z "$PASSWD" ] && errex "Password must not be empty"
+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 "$USER" -p "$PASSWD")"
+
+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
+  grep -qi "^$(escape "${USER}")|" "${DATABASE}" 2>/dev/null || errex "User \"${USER}\" does not exist"
+  sed -i "s ^""${USER}""|.* ""${USER}""|""${HASH}"" " "${DATABASE}"
+) 200< "${DATABASE}"
diff --git a/target/bin/virus-wiper b/target/bin/virus-wiper
old mode 100644
new mode 100755
index 279085ba..2c6c9762
--- a/target/bin/virus-wiper
+++ b/target/bin/virus-wiper
@@ -1,3 +1,3 @@
-#!/bin/bash
+#! /bin/bash
 
-find /var/lib/amavis/virusmails/ -type f -mtime +$VIRUSMAILS_DELETE_DELAY -delete
+find /var/lib/amavis/virusmails/ -type f -mtime +"${VIRUSMAILS_DELETE_DELAY}" -delete
diff --git a/target/check-for-changes.sh b/target/check-for-changes.sh
index d1808d54..c36c1693 100755
--- a/target/check-for-changes.sh
+++ b/target/check-for-changes.sh
@@ -1,11 +1,11 @@
-#!/bin/bash
+#! /bin/bash
 
 # version  0.2.0
 #
 # <INSERT TASK HERE>
 
-# shellcheck source=/dev/null
-. /usr/local/bin/helper_functions.sh
+# shellcheck source=./helper-functions.sh
+. /usr/local/bin/helper-functions.sh
 
 LOG_DATE=$(date +"%Y-%m-%d %H:%M:%S ")
 echo "${LOG_DATE} Start check-for-changes script."
diff --git a/target/fail2ban-wrapper.sh b/target/fail2ban-wrapper.sh
old mode 100644
new mode 100755
index a786eb2c..45633477
--- a/target/fail2ban-wrapper.sh
+++ b/target/fail2ban-wrapper.sh
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#! /bin/bash
 
 # version  0.1.0
 #
diff --git a/target/helper_functions.sh b/target/helper-functions.sh
old mode 100644
new mode 100755
similarity index 99%
rename from target/helper_functions.sh
rename to target/helper-functions.sh
index f2ac258f..b619b956
--- a/target/helper_functions.sh
+++ b/target/helper-functions.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#! /bin/bash
 
 # version  0.1.1
 #
diff --git a/target/postfix-wrapper.sh b/target/postfix-wrapper.sh
old mode 100644
new mode 100755
index 981d8f07..7c1bb3b8
--- a/target/postfix-wrapper.sh
+++ b/target/postfix-wrapper.sh
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#! /bin/bash
 
 # version  0.1.0
 #
diff --git a/target/postsrsd-wrapper.sh b/target/postsrsd-wrapper.sh
old mode 100644
new mode 100755
index cc33684a..61a23094
--- a/target/postsrsd-wrapper.sh
+++ b/target/postsrsd-wrapper.sh
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#! /bin/bash
 
 # version  0.1.0
 
diff --git a/target/start-mailserver.sh b/target/start-mailserver.sh
old mode 100644
new mode 100755
index 8ec3fb92..16dd7d95
--- a/target/start-mailserver.sh
+++ b/target/start-mailserver.sh
@@ -1,6 +1,6 @@
-#!/bin/bash
+#! /bin/bash
 
-# version  0.2.0
+# version  0.2.1
 #
 # Starts the mailserver.
 
@@ -49,7 +49,7 @@ DEFAULT_VARS["SPAMASSASSIN_SPAM_TO_INBOX"]="${SPAMASSASSIN_SPAM_TO_INBOX:=0}"
 DEFAULT_VARS["MOVE_SPAM_TO_JUNK"]="${MOVE_SPAM_TO_JUNK:=1}"
 DEFAULT_VARS["VIRUSMAILS_DELETE_DELAY"]="${VIRUSMAILS_DELETE_DELAY:=7}"
 DEFAULT_VARS["NETWORK_INTERFACE"]="${NETWORK_INTERFACE:="eth0"}"
-# DEFAULT_VARS["DMS_DEBUG"] defined in helper_functions.sh
+# DEFAULT_VARS["DMS_DEBUG"] defined in helper-functions.sh
 
 ##########################################################################
 # << DEFAULT VARS
@@ -2088,8 +2088,8 @@ function _start_changedetector
 # !  CARE --> DON'T CHANGE, unless you exactly know what you are doing
 # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-# shellcheck source=/dev/null
-. /usr/local/bin/helper_functions.sh
+# shellcheck source=./helper-functions.sh
+. /usr/local/bin/helper-functions.sh
 
 if [[ ${DEFAULT_VARS["DMS_DEBUG"]} -eq 1 ]]
 then
diff --git a/test/helper_functions.bats b/test/helper_functions.bats
index 49f1819f..4700908d 100644
--- a/test/helper_functions.bats
+++ b/test/helper_functions.bats
@@ -2,7 +2,7 @@ load 'test_helper/bats-support/load'
 load 'test_helper/bats-assert/load'
 
 # load the helper function into current context
-. ./target/helper_functions.sh
+. ./target/helper-functions.sh
 
 @test "check helper function: _sanitize_ipv4_to_subnet_cidr" {
     output=$(_sanitize_ipv4_to_subnet_cidr 255.255.255.255/0)
@@ -11,4 +11,4 @@ load 'test_helper/bats-assert/load'
     assert_output "192.168.240.0/20"
     output=$(_sanitize_ipv4_to_subnet_cidr 192.168.255.14/32)
     assert_output "192.168.255.14/32"
-}
\ No newline at end of file
+}
diff --git a/test/linting/lint.sh b/test/linting/lint.sh
index 56f45e0e..b56a78e9 100755
--- a/test/linting/lint.sh
+++ b/test/linting/lint.sh
@@ -81,7 +81,8 @@ function __which { command -v "${@}" &>/dev/null ; }
 
 function _eclint
 {
-  local LINT=(eclint -exclude "(.*\.git.*|.*\.md$|\.bats$)")
+  local SCRIPT='EDITORCONFIG LINTER'
+  local LINT=(eclint -exclude "(.*\.git.*|.*\.md$|\.bats$|\.cf$|\.conf$|\.init$)")
 
   if ! __in_path "${LINT[0]}"
   then
@@ -93,7 +94,6 @@ function _eclint
     'type: editorconfig' \
     '(linter version:' "$(${LINT[0]} --version))"
 
-  local SCRIPT='EDITORCONFIG LINTER'
   if "${LINT[@]}"
   then
     __log_success 'no errors detected'
@@ -105,6 +105,7 @@ function _eclint
 
 function _hadolint
 {
+  local SCRIPT='HADOLINT'
   local LINT=(hadolint -c "${CDIR}/.hadolint.yaml")
 
   if ! __in_path "${LINT[0]}"
@@ -117,7 +118,6 @@ function _hadolint
     'type: Dockerfile' \
     '(linter version:' "$(${LINT[0]} --version | grep -E -o "v[0-9\.]*"))"
 
-  local SCRIPT='HADOLINT'
   if git ls-files --exclude='Dockerfile*' --ignored | \
     xargs --max-lines=1 "${LINT[@]}"
   then
@@ -130,7 +130,9 @@ function _hadolint
 
 function _shellcheck
 {
-  local LINT=(/usr/bin/shellcheck -S style -Cauto -o all -e SC2154 -W 50)
+  local SCRIPT='SHELLCHECK'
+  local ERR=0
+  local LINT=(/usr/bin/shellcheck -x -S style -Cauto -o all -e SC2154 -W 50)
 
   if ! __in_path "${LINT[0]}"
   then
@@ -142,17 +144,44 @@ function _shellcheck
     'type: shellcheck' '(linter version:' \
     "$(${LINT[0]} --version | grep -m 2 -o "[0-9.]*"))"
 
-  local FIND=(
-    find . -iname "*.sh"
-    -not -path "./test/*"
-    -not -path "./target/docker-configomat/*"
-    -exec "${LINT[@]}" {} \;)
+  # an overengineered solution to allow shellcheck -x to
+  # properly follow `source=<SOURCE FILE>` when sourcing
+  # files with `. <FILE>` in shell scripts.
+  while read -r FILE
+  do
+    if ! (
+      cd "$(realpath "$(dirname "$(readlink -f "${FILE}")")")"
+      if ! "${LINT[@]}" "$(basename -- "${FILE}")"
+      then
+        return 1
+      fi
+    )
+    then
+      ERR=1
+    fi
+  done < <(find . -type f -iname "*.sh" \
+    -not -path "./test/bats/*" \
+    -not -path "./test/test_helper/*" \
+    -not -path "./target/docker-configomat/*")
 
-  local SCRIPT='SHELLCHECK'
-  if "${FIND[@]}" | grep -q .
+  # the same for executables in target/bin/
+  while read -r FILE
+  do
+    if ! (
+      cd "$(realpath "$(dirname "$(readlink -f "${FILE}")")")"
+      if ! "${LINT[@]}" "$(basename -- "${FILE}")"
+      then
+        return 1
+      fi
+    )
+    then
+      ERR=1
+    fi
+  done < <(find target/bin -executable -type f)
+
+  if [[ ERR -eq 1 ]]
   then
-    "${FIND[@]}"
-    __log_abort
+    __log_abort 'errors encountered'
     return 101
   else
     __log_success 'no errors detected'
diff --git a/test/mail_fail2ban.bats b/test/mail_fail2ban.bats
index 7b213c24..f00f1392 100644
--- a/test/mail_fail2ban.bats
+++ b/test/mail_fail2ban.bats
@@ -25,7 +25,7 @@ function setup_file() {
         tail -f /var/log/faillog
 
     wait_for_finished_setup_in_container mail_fail2ban
-    
+
 }
 
 function teardown_file() {
@@ -125,11 +125,11 @@ function teardown_file() {
   run docker exec mail_fail2ban /bin/sh -c "fail2ban-client set dovecot banip 192.0.66.5"
   sleep 10
   run ./setup.sh -c mail_fail2ban debug fail2ban
-  assert_output --regexp "^Banned in dovecot: 192.0.66.5 192.0.66.4.*"
+  assert_output -p "Banned in dovecot: 192.0.66.5" -p "Banned in dovecot: 192.0.66.4"
   run ./setup.sh -c mail_fail2ban debug fail2ban unban 192.0.66.4
   assert_output --partial "unbanned IP from dovecot: 192.0.66.4"
   run ./setup.sh -c mail_fail2ban debug fail2ban
-  assert_output --regexp "^Banned in dovecot: 192.0.66.5.*"
+  assert_output --partial "Banned in dovecot: 192.0.66.5"
   run ./setup.sh -c mail_fail2ban debug fail2ban unban 192.0.66.5
   run ./setup.sh -c mail_fail2ban debug fail2ban unban
   assert_output --partial "You need to specify an IP address. Run"
@@ -146,4 +146,4 @@ function teardown_file() {
 
 @test "last" {
   skip 'this test is only there to reliably mark the end for the teardown_file'
-}
\ No newline at end of file
+}