diff --git a/test/docker-openldap/Dockerfile b/test/config/ldap/docker-openldap/Dockerfile
similarity index 100%
rename from test/docker-openldap/Dockerfile
rename to test/config/ldap/docker-openldap/Dockerfile
diff --git a/test/docker-openldap/bootstrap/ldif/01_mail-tree.ldif b/test/config/ldap/docker-openldap/bootstrap/ldif/01_mail-tree.ldif
similarity index 100%
rename from test/docker-openldap/bootstrap/ldif/01_mail-tree.ldif
rename to test/config/ldap/docker-openldap/bootstrap/ldif/01_mail-tree.ldif
diff --git a/test/docker-openldap/bootstrap/ldif/02_user-email.ldif b/test/config/ldap/docker-openldap/bootstrap/ldif/02_user-email.ldif
similarity index 100%
rename from test/docker-openldap/bootstrap/ldif/02_user-email.ldif
rename to test/config/ldap/docker-openldap/bootstrap/ldif/02_user-email.ldif
diff --git a/test/docker-openldap/bootstrap/ldif/03_user-email-other-primary-domain.ldif b/test/config/ldap/docker-openldap/bootstrap/ldif/03_user-email-other-primary-domain.ldif
similarity index 100%
rename from test/docker-openldap/bootstrap/ldif/03_user-email-other-primary-domain.ldif
rename to test/config/ldap/docker-openldap/bootstrap/ldif/03_user-email-other-primary-domain.ldif
diff --git a/test/docker-openldap/bootstrap/ldif/04_user-email-different-uid.ldif b/test/config/ldap/docker-openldap/bootstrap/ldif/04_user-email-different-uid.ldif
similarity index 100%
rename from test/docker-openldap/bootstrap/ldif/04_user-email-different-uid.ldif
rename to test/config/ldap/docker-openldap/bootstrap/ldif/04_user-email-different-uid.ldif
diff --git a/test/docker-openldap/bootstrap/schema/mmc/postfix-book.schema b/test/config/ldap/docker-openldap/bootstrap/schema/mmc/postfix-book.schema
similarity index 100%
rename from test/docker-openldap/bootstrap/schema/mmc/postfix-book.schema
rename to test/config/ldap/docker-openldap/bootstrap/schema/mmc/postfix-book.schema
diff --git a/test/config/ldap-aliases.cf b/test/config/ldap/overrides/ldap-aliases.cf
similarity index 100%
rename from test/config/ldap-aliases.cf
rename to test/config/ldap/overrides/ldap-aliases.cf
diff --git a/test/config/ldap-groups.cf b/test/config/ldap/overrides/ldap-groups.cf
similarity index 100%
rename from test/config/ldap-groups.cf
rename to test/config/ldap/overrides/ldap-groups.cf
diff --git a/test/config/ldap-users.cf b/test/config/ldap/overrides/ldap-users.cf
similarity index 100%
rename from test/config/ldap-users.cf
rename to test/config/ldap/overrides/ldap-users.cf
diff --git a/test/tests/serial/mail_with_ldap.bats b/test/tests/serial/mail_with_ldap.bats
index 75768bbb..57251aa1 100644
--- a/test/tests/serial/mail_with_ldap.bats
+++ b/test/tests/serial/mail_with_ldap.bats
@@ -1,245 +1,313 @@
-load "${REPOSITORY_ROOT}/test/test_helper/common"
+load "${REPOSITORY_ROOT}/test/helper/setup"
+load "${REPOSITORY_ROOT}/test/helper/common"
+
+BATS_TEST_NAME_PREFIX='[LDAP] '
+CONTAINER1_NAME='dms-test_ldap'
+CONTAINER2_NAME='dms-test_ldap_provider'
 
 function setup_file() {
-  pushd test/docker-openldap/ || return 1
-  docker build -f Dockerfile -t ldap --no-cache .
-  popd || return 1
-
-  export DOMAIN='my-domain.com'
+  export DMS_TEST_NETWORK='test-network-ldap'
+  export DOMAIN='example.test'
   export FQDN_MAIL="mail.${DOMAIN}"
   export FQDN_LDAP="ldap.${DOMAIN}"
+  # LDAP is provisioned with two domains (via `.ldif` files) unrelated to the FQDN of DMS:
   export FQDN_LOCALHOST_A='localhost.localdomain'
   export FQDN_LOCALHOST_B='localhost.otherdomain'
-  export DMS_TEST_NETWORK='test-network-ldap'
 
+  # Link the test containers to separate network:
   # NOTE: If the network already exists, test will fail to start.
   docker network create "${DMS_TEST_NETWORK}"
 
-  docker run -d --name ldap_for_mail \
+  # Setup local openldap service:
+  # NOTE: Building via Dockerfile is required? Image won't accept read-only if it needs to adjust permissions for bootstrap files.
+  # TODO: Upstream image is no longer maintained, may want to migrate?
+  docker build -t dms-openldap test/config/ldap/docker-openldap/
+
+  docker run -d --name "${CONTAINER2_NAME}" \
     --env LDAP_DOMAIN="${FQDN_LOCALHOST_A}" \
-    --network "${DMS_TEST_NETWORK}" \
-    --network-alias 'ldap' \
     --hostname "${FQDN_LDAP}" \
-    --tty \
-    ldap # Image name
-
-  # _setup_ldap uses _replace_by_env_in_file with ENV vars like DOVECOT_TLS with a prefix (eg. DOVECOT_ or LDAP_)
-  local PRIVATE_CONFIG
-  PRIVATE_CONFIG=$(duplicate_config_for_container .)
-  docker run -d --name mail_with_ldap \
-    -v "${PRIVATE_CONFIG}:/tmp/docker-mailserver" \
-    -v "$(pwd)/test/test-files:/tmp/docker-mailserver-test:ro" \
-    -e DOVECOT_PASS_FILTER="(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))" \
-    -e DOVECOT_TLS=no \
-    -e DOVECOT_USER_FILTER="(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))" \
-    -e ACCOUNT_PROVISIONER=LDAP \
-    -e PFLOGSUMM_TRIGGER=logrotate \
-    -e ENABLE_SASLAUTHD=1 \
-    -e LDAP_BIND_DN=cn=admin,dc=localhost,dc=localdomain \
-    -e LDAP_BIND_PW=admin \
-    -e LDAP_QUERY_FILTER_ALIAS="(|(&(mailAlias=%s)(objectClass=PostfixBookMailForward))(&(mailAlias=%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE)))" \
-    -e LDAP_QUERY_FILTER_DOMAIN="(|(&(mail=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailGroupMember=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailalias=*@%s)(objectClass=PostfixBookMailForward)))" \
-    -e LDAP_QUERY_FILTER_GROUP="(&(mailGroupMember=%s)(mailEnabled=TRUE))" \
-    -e LDAP_QUERY_FILTER_SENDERS="(|(&(mail=%s)(mailEnabled=TRUE))(&(mailGroupMember=%s)(mailEnabled=TRUE))(|(&(mailAlias=%s)(objectClass=PostfixBookMailForward))(&(mailAlias=%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE)))(uniqueIdentifier=some.user.id))" \
-    -e LDAP_QUERY_FILTER_USER="(&(mail=%s)(mailEnabled=TRUE))" \
-    -e LDAP_START_TLS=no \
-    -e LDAP_SEARCH_BASE=ou=people,dc=localhost,dc=localdomain \
-    -e LDAP_SERVER_HOST=ldap \
-    -e PERMIT_DOCKER=container \
-    -e POSTMASTER_ADDRESS="postmaster@${FQDN_LOCALHOST_A}" \
-    -e REPORT_RECIPIENT=1 \
-    -e SASLAUTHD_MECHANISMS=ldap \
-    -e SPOOF_PROTECTION=1 \
-    -e SSL_TYPE='snakeoil' \
     --network "${DMS_TEST_NETWORK}" \
-    --hostname "${FQDN_MAIL}" \
-    --tty \
-    "${NAME}" # Image name
+    dms-openldap
 
-  wait_for_smtp_port_in_container mail_with_ldap
+  #
+  # Setup DMS container
+  #
+
+  local ENV_LDAP_CONFIG=(
+    # Configure for LDAP account provisioner and alternative to Dovecot SASL:
+    --env ACCOUNT_PROVISIONER=LDAP
+    --env ENABLE_SASLAUTHD=1
+    --env SASLAUTHD_MECHANISMS=ldap
+
+    # ENV to configure LDAP configs for Dovecot + Postfix:
+    # NOTE: `scripts/startup/setup.d/ldap.sh:_setup_ldap()` uses `_replace_by_env_in_file()` to configure settings (stripping `DOVECOT_` / `LDAP_` prefixes):
+    # Dovecot:
+    --env DOVECOT_PASS_FILTER='(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))'
+    --env DOVECOT_TLS=no
+    --env DOVECOT_USER_FILTER='(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))'
+    # Postfix:
+    --env LDAP_BIND_DN='cn=admin,dc=localhost,dc=localdomain'
+    --env LDAP_BIND_PW='admin'
+    --env LDAP_QUERY_FILTER_ALIAS='(|(&(mailAlias=%s)(objectClass=PostfixBookMailForward))(&(mailAlias=%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE)))'
+    --env LDAP_QUERY_FILTER_DOMAIN='(|(&(mail=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailGroupMember=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailalias=*@%s)(objectClass=PostfixBookMailForward)))'
+    --env LDAP_QUERY_FILTER_GROUP='(&(mailGroupMember=%s)(mailEnabled=TRUE))'
+    --env LDAP_QUERY_FILTER_SENDERS='(|(&(mail=%s)(mailEnabled=TRUE))(&(mailGroupMember=%s)(mailEnabled=TRUE))(|(&(mailAlias=%s)(objectClass=PostfixBookMailForward))(&(mailAlias=%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE)))(uniqueIdentifier=some.user.id))'
+    --env LDAP_QUERY_FILTER_USER='(&(mail=%s)(mailEnabled=TRUE))'
+    --env LDAP_SEARCH_BASE='ou=people,dc=localhost,dc=localdomain'
+    --env LDAP_SERVER_HOST="${FQDN_LDAP}"
+    --env LDAP_START_TLS=no
+  )
+
+  # Extra ENV needed to support specific testcases:
+  local ENV_SUPPORT=(
+    --env PERMIT_DOCKER=container # Required for attempting SMTP auth on port 25 via nc
+    # Required for openssl commands to be successul:
+    # NOTE: snakeoil cert is created (for `docker-mailserver.invalid`) via Debian post-install script for Postfix package.
+    # TODO: Use proper TLS cert
+    --env SSL_TYPE='snakeoil'
+
+    # TODO; All below are questionable value to LDAP tests?
+    --env POSTMASTER_ADDRESS="postmaster@${FQDN_LOCALHOST_A}" # TODO: Only required because LDAP accounts use unrelated domain part. FQDN_LOCALHOST_A / ldif files can be adjusted to FQDN_MAIL
+    --env PFLOGSUMM_TRIGGER=logrotate
+    --env REPORT_RECIPIENT=1 # TODO: Invalid value, should be a recipient address (if not default postmaster), remove?
+    --env SPOOF_PROTECTION=1
+  )
+
+  local CUSTOM_SETUP_ARGUMENTS=(
+    --hostname "${FQDN_MAIL}"
+    --network "${DMS_TEST_NETWORK}"
+
+    "${ENV_LDAP_CONFIG[@]}"
+    "${ENV_SUPPORT[@]}"
+  )
+
+  # Set default implicit container fallback for helpers:
+  export CONTAINER_NAME=${CONTAINER1_NAME}
+
+  _init_with_defaults
+  # NOTE: `test/config/` has now been duplicated, can move test specific files to host-side `/tmp/docker-mailserver`:
+  mv "${TEST_TMP_CONFIG}/ldap/overrides/"*.cf "${TEST_TMP_CONFIG}/"
+  _common_container_setup 'CUSTOM_SETUP_ARGUMENTS'
+  _wait_for_smtp_port_in_container
 }
 
 function teardown_file() {
-  docker rm -f ldap_for_mail mail_with_ldap
+  docker rm -f "${CONTAINER1_NAME}" "${CONTAINER2_NAME}"
   docker network rm "${DMS_TEST_NETWORK}"
 }
 
 # postfix
-@test "checking postfix: ldap lookup works correctly" {
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q some.user@${FQDN_LOCALHOST_A} ldap:/etc/postfix/ldap-users.cf"
-  assert_success
-  assert_output "some.user@${FQDN_LOCALHOST_A}"
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q postmaster@${FQDN_LOCALHOST_A} ldap:/etc/postfix/ldap-aliases.cf"
-  assert_success
-  assert_output "some.user@${FQDN_LOCALHOST_A}"
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q employees@${FQDN_LOCALHOST_A} ldap:/etc/postfix/ldap-groups.cf"
-  assert_success
-  assert_output "some.user@${FQDN_LOCALHOST_A}"
-
-  # Test of the user part of the domain is not the same as the uniqueIdentifier part in the ldap
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q some.user.email@${FQDN_LOCALHOST_A} ldap:/etc/postfix/ldap-users.cf"
-  assert_success
-  assert_output "some.user.email@${FQDN_LOCALHOST_A}"
+# NOTE: Each of the 3 user accounts tested below are defined in separate LDIF config files,
+# Those are bundled into the locally built OpenLDAP Dockerfile.
+@test "postfix: ldap lookup works correctly" {
+  _should_exist_in_ldap_tables "some.user@${FQDN_LOCALHOST_A}"
 
   # Test email receiving from a other domain then the primary domain of the mailserver
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q some.other.user@${FQDN_LOCALHOST_B} ldap:/etc/postfix/ldap-users.cf"
+  _should_exist_in_ldap_tables "some.other.user@${FQDN_LOCALHOST_B}"
+
+  # Should not require `uniqueIdentifier` to match the local part of `mail` (`.ldif` defined settings):
+  # REF: https://github.com/docker-mailserver/docker-mailserver/pull/642#issuecomment-313916384
+  # NOTE: This account has no `mailAlias` or `mailGroupMember` defined in it's `.ldif`.
+  local MAIL_ACCOUNT="some.user.email@${FQDN_LOCALHOST_A}"
+  _run_in_container postmap -q "${MAIL_ACCOUNT}" ldap:/etc/postfix/ldap-users.cf
   assert_success
-  assert_output "some.other.user@${FQDN_LOCALHOST_B}"
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q postmaster@${FQDN_LOCALHOST_B} ldap:/etc/postfix/ldap-aliases.cf"
-  assert_success
-  assert_output "some.other.user@${FQDN_LOCALHOST_B}"
-  run docker exec mail_with_ldap /bin/sh -c "postmap -q employees@${FQDN_LOCALHOST_B} ldap:/etc/postfix/ldap-groups.cf"
-  assert_success
-  assert_output "some.other.user@${FQDN_LOCALHOST_B}"
+  assert_output "${MAIL_ACCOUNT}"
 }
 
-@test "checking postfix: ldap custom config files copied" {
-  run docker exec mail_with_ldap /bin/sh -c "grep '# Testconfig for ldap integration' /etc/postfix/ldap-users.cf"
-  assert_success
+# Custom LDAP config files support:
+# TODO: Compare to provided configs and if they're just including a test comment,
+# could just copy the config and append without carrying a separate test config?
+@test "postfix: ldap custom config files copied" {
+  local LDAP_CONFIGS_POSTFIX=(
+    /etc/postfix/ldap-users.cf
+    /etc/postfix/ldap-groups.cf
+    /etc/postfix/ldap-aliases.cf
+  )
 
-  run docker exec mail_with_ldap /bin/sh -c "grep '# Testconfig for ldap integration' /etc/postfix/ldap-groups.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep '# Testconfig for ldap integration' /etc/postfix/ldap-aliases.cf"
-  assert_success
+  for LDAP_CONFIG in "${LDAP_CONFIGS_POSTFIX[@]}"; do
+    _run_in_container grep '# Testconfig for ldap integration' "${LDAP_CONFIG}"
+    assert_success
+  done
 }
 
-@test "checking postfix: ldap config overwrites success" {
-  run docker exec mail_with_ldap /bin/sh -c "grep 'server_host = ldap' /etc/postfix/ldap-users.cf"
-  assert_success
+@test "postfix: ldap config overwrites success" {
+  local LDAP_SETTINGS_POSTFIX=(
+    "server_host = ${FQDN_LDAP}"
+    'start_tls = no'
+    'search_base = ou=people,dc=localhost,dc=localdomain'
+    'bind_dn = cn=admin,dc=localhost,dc=localdomain'
+  )
 
-  run docker exec mail_with_ldap /bin/sh -c "grep 'start_tls = no' /etc/postfix/ldap-users.cf"
-  assert_success
+  for LDAP_SETTING in "${LDAP_SETTINGS_POSTFIX[@]}"; do
+    # "${LDAP_SETTING%=*}" is to match only the key portion of the var (helpful for assert_output error messages)
+    # NOTE: `start_tls = no` is a default setting, but the white-space differs when ENV `LDAP_START_TLS` is not set explicitly.
+    _run_in_container grep "${LDAP_SETTING%=*}" /etc/postfix/ldap-users.cf
+    assert_output "${LDAP_SETTING}"
+    assert_success
 
-  run docker exec mail_with_ldap /bin/sh -c "grep 'search_base = ou=people,dc=localhost,dc=localdomain' /etc/postfix/ldap-users.cf"
-  assert_success
+    _run_in_container grep "${LDAP_SETTING%=*}" /etc/postfix/ldap-groups.cf
+    assert_output "${LDAP_SETTING}"
+    assert_success
 
-  run docker exec mail_with_ldap /bin/sh -c "grep 'bind_dn = cn=admin,dc=localhost,dc=localdomain' /etc/postfix/ldap-users.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'server_host = ldap' /etc/postfix/ldap-groups.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'start_tls = no' /etc/postfix/ldap-groups.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'search_base = ou=people,dc=localhost,dc=localdomain' /etc/postfix/ldap-groups.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'bind_dn = cn=admin,dc=localhost,dc=localdomain' /etc/postfix/ldap-groups.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'server_host = ldap' /etc/postfix/ldap-aliases.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'start_tls = no' /etc/postfix/ldap-aliases.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'search_base = ou=people,dc=localhost,dc=localdomain' /etc/postfix/ldap-aliases.cf"
-  assert_success
-
-  run docker exec mail_with_ldap /bin/sh -c "grep 'bind_dn = cn=admin,dc=localhost,dc=localdomain' /etc/postfix/ldap-aliases.cf"
-  assert_success
+    _run_in_container grep "${LDAP_SETTING%=*}" /etc/postfix/ldap-aliases.cf
+    assert_output "${LDAP_SETTING}"
+    assert_success
+  done
 }
 
 # dovecot
-@test "checking dovecot: ldap imap connection and authentication works" {
-  run docker exec mail_with_ldap /bin/sh -c "nc -w 1 0.0.0.0 143 < /tmp/docker-mailserver-test/auth/imap-ldap-auth.txt"
+@test "dovecot: ldap imap connection and authentication works" {
+  _run_in_container_bash 'nc -w 1 0.0.0.0 143 < /tmp/docker-mailserver-test/auth/imap-ldap-auth.txt'
   assert_success
 }
 
-@test "checking dovecot: ldap mail delivery works" {
-  run docker exec mail_with_ldap /bin/sh -c "sendmail -f user@external.tld some.user@${FQDN_LOCALHOST_A} < /tmp/docker-mailserver-test/email-templates/test-email.txt"
-  sleep 10
-  run docker exec mail_with_ldap /bin/sh -c "grep -R 'This is a test mail.' /var/mail/${FQDN_LOCALHOST_A}/some.user/new/ | wc -l"
-  assert_success
-  assert_output 1
+@test "dovecot: ldap mail delivery works" {
+  _should_successfully_deliver_mail_to "some.user@${FQDN_LOCALHOST_A}" "/var/mail/${FQDN_LOCALHOST_A}/some.user/new/"
+
+  # Should support delivering to a local recipient with a different domain (and disjoint mail location):
+  # NOTE: Mail is delivered to location defined in `.ldif` (an account config setting, either `mailHomeDirectory` or `mailStorageDirectory`).
+  # `some.other.user` has been configured to use a mailbox domain different from it's address domain part, hence the difference here:
+  _should_successfully_deliver_mail_to "some.other.user@${FQDN_LOCALHOST_B}" "/var/mail/${FQDN_LOCALHOST_A}/some.other.user/new/"
 }
 
-@test "checking dovecot: ldap mail delivery works for a different domain then the mailserver" {
-  run docker exec mail_with_ldap /bin/sh -c "sendmail -f user@external.tld some.other.user@${FQDN_LOCALHOST_B} < /tmp/docker-mailserver-test/email-templates/test-email.txt"
-  sleep 10
-  run docker exec mail_with_ldap /bin/sh -c "ls -A /var/mail/${FQDN_LOCALHOST_A}/some.other.user/new | wc -l"
-  assert_success
-  assert_output 1
+@test "dovecot: ldap config overwrites success" {
+  local LDAP_SETTINGS_DOVECOT=(
+    "uris = ldap://${FQDN_LDAP}"
+    'tls = no'
+    'base = ou=people,dc=localhost,dc=localdomain'
+    'dn = cn=admin,dc=localhost,dc=localdomain'
+  )
+
+  for LDAP_SETTING in "${LDAP_SETTINGS_DOVECOT[@]}"; do
+    _run_in_container grep "${LDAP_SETTING%=*}" /etc/dovecot/dovecot-ldap.conf.ext
+    assert_output "${LDAP_SETTING}"
+    assert_success
+  done
 }
 
-@test "checking dovecot: ldap config overwrites success" {
-  run docker exec mail_with_ldap /bin/sh -c "grep 'uris = ldap://ldap' /etc/dovecot/dovecot-ldap.conf.ext"
-  assert_success
-  run docker exec mail_with_ldap /bin/sh -c "grep 'tls = no' /etc/dovecot/dovecot-ldap.conf.ext"
-  assert_success
-  run docker exec mail_with_ldap /bin/sh -c "grep 'base = ou=people,dc=localhost,dc=localdomain' /etc/dovecot/dovecot-ldap.conf.ext"
-  assert_success
-  run docker exec mail_with_ldap /bin/sh -c "grep 'dn = cn=admin,dc=localhost,dc=localdomain' /etc/dovecot/dovecot-ldap.conf.ext"
+# Requires ENV `POSTMASTER_ADDRESS`
+# NOTE: Not important to LDAP feature tests?
+@test "dovecot: postmaster address" {
+  _run_in_container grep "postmaster_address = postmaster@${FQDN_LOCALHOST_A}" /etc/dovecot/conf.d/15-lda.conf
   assert_success
 }
 
-@test "checking dovecot: postmaster address" {
-  run docker exec mail_with_ldap /bin/sh -c "grep 'postmaster_address = postmaster@${FQDN_LOCALHOST_A}' /etc/dovecot/conf.d/15-lda.conf"
-  assert_success
-}
-
-@test "checking dovecot: quota plugin is disabled" {
- run docker exec mail_with_ldap /bin/sh -c "grep '\$mail_plugins quota' /etc/dovecot/conf.d/10-mail.conf"
- assert_failure
- run docker exec mail_with_ldap /bin/sh -c "grep '\$mail_plugins imap_quota' /etc/dovecot/conf.d/20-imap.conf"
- assert_failure
- run docker exec mail_with_ldap ls /etc/dovecot/conf.d/90-quota.conf
- assert_failure
- run docker exec mail_with_ldap ls /etc/dovecot/conf.d/90-quota.conf.disab
- assert_success
-}
-
-@test "checking postfix: dovecot quota absent in postconf" {
-  run docker exec mail_with_ldap /bin/bash -c "postconf | grep 'check_policy_service inet:localhost:65265'"
+# NOTE: `target/scripts/startup/setup.d/dovecot.sh` should prevent enabling the quotas feature when using LDAP:
+@test "dovecot: quota plugin is disabled" {
+  # Dovecot configs have not enabled the quota plugins:
+  _run_in_container grep "\$mail_plugins quota" /etc/dovecot/conf.d/10-mail.conf
   assert_failure
+  _run_in_container grep "\$mail_plugins imap_quota" /etc/dovecot/conf.d/20-imap.conf
+  assert_failure
+
+  # Dovecot Quota config only present with disabled extension:
+  _run_in_container_bash '[[ -f /etc/dovecot/conf.d/90-quota.conf ]]'
+  assert_failure
+  _run_in_container_bash '[[ -f /etc/dovecot/conf.d/90-quota.conf.disab ]]'
+  assert_success
+
+  # Postfix quotas policy service not configured in `main.cf`:
+  _run_in_container postconf smtpd_recipient_restrictions
+  refute_output --partial 'check_policy_service inet:localhost:65265'
 }
 
-@test "checking spoofing (with LDAP): rejects sender forging" {
-  wait_for_smtp_port_in_container_to_respond mail_with_ldap
-  run docker exec mail_with_ldap /bin/sh -c "openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed.txt | grep 'Sender address rejected: not owned by user'"
+@test "saslauthd: sasl ldap authentication works" {
+  _run_in_container testsaslauthd -u some.user -p secret
   assert_success
 }
 
-# ATTENTION: these tests must come after "checking dovecot: ldap mail delivery works" since they will deliver an email which skews the count in said test, leading to failure
-@test "checking spoofing: accepts sending as alias (with LDAP)" {
-  run docker exec mail_with_ldap /bin/sh -c "openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed-alias.txt | grep 'End data with'"
+# Requires ENV `PFLOGSUMM_TRIGGER=logrotate`
+@test "pflogsumm delivery" {
+  # Verify default sender is `mailserver-report` when ENV `PFLOGSUMM_SENDER` + `REPORT_SENDER` are unset:
+  # NOTE: Mail is sent from Postfix (configured hostname used as domain part)
+  _run_in_container grep "mailserver-report@${FQDN_MAIL}" /etc/logrotate.d/maillog
+  assert_success
+
+  # When `LOGROTATE_INTERVAL` is unset, the default should be configured as `weekly`:
+  _run_in_container grep 'weekly' /etc/logrotate.d/maillog
   assert_success
 }
-@test "checking spoofing: uses senders filter" {
+
+# ATTENTION: Remaining tests must come after "dovecot: ldap mail delivery works" since the below tests would affect the expected count (by delivering extra mail),
+# Thus not friendly for running testcases in this file in parallel
+
+# Requires ENV `SPOOF_PROTECTION=1` for the expected assert_output
+@test "spoofing (with LDAP): rejects sender forging" {
+  _wait_for_smtp_port_in_container_to_respond dms-test_ldap
+
+  _run_in_container_bash 'openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed.txt'
+  assert_output --partial 'Sender address rejected: not owned by user'
+}
+
+@test "spoofing (with LDAP): accepts sending as alias" {
+  _run_in_container_bash 'openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed-alias.txt'
+  assert_output --partial 'End data with'
+}
+
+@test "spoofing (with LDAP): uses senders filter" {
   # skip introduced with #3006, changing port 25 to 465
+  # Template used has invalid AUTH: https://github.com/docker-mailserver/docker-mailserver/pull/3006#discussion_r1073321432
   skip 'TODO: This test seems to have been broken from the start (?)'
-  
-  run docker exec mail_with_ldap /bin/sh -c "openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed-sender-with-filter-exception.txt | grep 'Sender address rejected: not owned by user'"
-  assert_success
+
+  _run_in_container_bash 'openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/ldap-smtp-auth-spoofed-sender-with-filter-exception.txt'
+  assert_output --partial 'Sender address rejected: not owned by user'
 }
 
-# saslauthd
-@test "checking saslauthd: sasl ldap authentication works" {
-  run docker exec mail_with_ldap bash -c "testsaslauthd -u some.user -p secret"
-  assert_success
-}
+@test "saslauthd: ldap smtp authentication" {
+  # Requires ENV `PERMIT_DOCKER=container`
+  _send_email 'auth/sasl-ldap-smtp-auth' '-w 5 0.0.0.0 25'
+  assert_output --partial 'Error: authentication not enabled'
 
-@test "checking saslauthd: ldap smtp authentication" {
-  run docker exec mail_with_ldap /bin/sh -c "nc -w 5 0.0.0.0 25 < /tmp/docker-mailserver-test/auth/sasl-ldap-smtp-auth.txt | grep 'Error: authentication not enabled'"
-  assert_success
-  run docker exec mail_with_ldap /bin/sh -c "openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/sasl-ldap-smtp-auth.txt | grep 'Authentication successful'"
-  assert_success
-  run docker exec mail_with_ldap /bin/sh -c "openssl s_client -quiet -starttls smtp -connect 0.0.0.0:587 < /tmp/docker-mailserver-test/auth/sasl-ldap-smtp-auth.txt | grep 'Authentication successful'"
-  assert_success
+  _run_in_container_bash 'openssl s_client -quiet -connect 0.0.0.0:465 < /tmp/docker-mailserver-test/auth/sasl-ldap-smtp-auth.txt'
+  assert_output --partial 'Authentication successful'
+
+  _run_in_container_bash 'openssl s_client -quiet -starttls smtp -connect 0.0.0.0:587 < /tmp/docker-mailserver-test/auth/sasl-ldap-smtp-auth.txt'
+  assert_output --partial 'Authentication successful'
 }
 
 #
-# Pflogsumm delivery check
+# Test helper methods:
 #
 
-@test "checking pflogsum delivery" {
-  # checking default sender is correctly set when env variable not defined
-  run docker exec mail_with_ldap grep "mailserver-report@${FQDN_MAIL}" /etc/logrotate.d/maillog
-  assert_success
+function _should_exist_in_ldap_tables() {
+  local MAIL_ACCOUNT=${1:?Mail account is required}
+  local DOMAIN_PART="${MAIL_ACCOUNT#*@}"
 
-  # checking default logrotation setup
-  run docker exec mail_with_ldap grep "weekly" /etc/logrotate.d/maillog
+  # Each LDAP config file sets `query_filter` to lookup a key in LDAP (values defined in `.ldif` test files)
+  # `mail` (ldap-users), `mailAlias` (ldap-aliases), `mailGroupMember` (ldap-groups)
+  # `postmap` is queried with the mail account address, and the LDAP service should respond with
+  # `result_attribute` which is the LDAP `mail` value (should match what we'r'e quering `postmap` with)
+
+  _run_in_container postmap -q "${MAIL_ACCOUNT}" ldap:/etc/postfix/ldap-users.cf
   assert_success
+  assert_output "${MAIL_ACCOUNT}"
+
+  # Check which account has the `postmaster` virtual alias:
+  _run_in_container postmap -q "postmaster@${DOMAIN_PART}" ldap:/etc/postfix/ldap-aliases.cf
+  assert_success
+  assert_output "${MAIL_ACCOUNT}"
+
+  _run_in_container postmap -q "employees@${DOMAIN_PART}" ldap:/etc/postfix/ldap-groups.cf
+  assert_success
+  assert_output "${MAIL_ACCOUNT}"
+}
+
+# NOTE: `test-email.txt` is only used for these two LDAP tests with `sendmail` command.
+# The file excludes sender/recipient addresses, thus not usable with `_send_email()` helper (`nc` command)?
+# TODO: Could probably adapt?
+function _should_successfully_deliver_mail_to() {
+  local SENDER_ADDRESS='user@external.tld'
+  local RECIPIENT_ADDRESS=${1:?Recipient address is required}
+  local MAIL_STORAGE_RECIPIENT=${2:?Recipient storage location is required}
+  local MAIL_TEMPLATE='/tmp/docker-mailserver-test/email-templates/test-email.txt'
+
+  _run_in_container_bash "sendmail -f ${SENDER_ADDRESS} ${RECIPIENT_ADDRESS} < ${MAIL_TEMPLATE}"
+  _wait_for_empty_mail_queue_in_container
+
+  _run_in_container grep -R 'This is a test mail.' "${MAIL_STORAGE_RECIPIENT}"
+  assert_success
+  _should_output_number_of_lines 1
+
+  # NOTE: Prevents compatibility for running testcases in parallel (for same container) when the count could become racey:
+  _count_files_in_directory_in_container "${MAIL_STORAGE_RECIPIENT}" 1
 }