diff --git a/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HostingAssetEntityValidatorRegistry.java b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HostingAssetEntityValidatorRegistry.java
index 6efbed70..5b287a14 100644
--- a/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HostingAssetEntityValidatorRegistry.java
+++ b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HostingAssetEntityValidatorRegistry.java
@@ -24,6 +24,7 @@ public class HostingAssetEntityValidatorRegistry {
         register(DOMAIN_DNS_SETUP, new HsDomainDnsSetupHostingAssetValidator());
         register(DOMAIN_HTTP_SETUP, new HsDomainHttpSetupHostingAssetValidator());
         register(DOMAIN_EMAIL_SUBMISSION_SETUP, new HsDomainEMailSubmissionSetupHostingAssetValidator());
+        register(DOMAIN_EMAIL_MAILBOX_SETUP, new HsDomainEMailMailboxSetupHostingAssetValidator());
     }
 
     private static void register(final Enum<HsHostingAssetType> type, final HsEntityValidator<HsHostingAssetEntity> validator) {
diff --git a/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEMailMailboxSetupHostingAssetValidator.java b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEMailMailboxSetupHostingAssetValidator.java
new file mode 100644
index 00000000..5e919b00
--- /dev/null
+++ b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEMailMailboxSetupHostingAssetValidator.java
@@ -0,0 +1,34 @@
+package net.hostsharing.hsadminng.hs.hosting.asset.validators;
+
+import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetEntity;
+
+import java.util.regex.Pattern;
+
+import static java.util.Optional.ofNullable;
+import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.DOMAIN_EMAIL_SUBMISSION_SETUP;
+
+class HsDomainEMailMailboxSetupHostingAssetValidator extends HostingAssetEntityValidator {
+
+    public static final String IDENTIFIER_SUFFIX = "|MBOX";
+
+    HsDomainEMailMailboxSetupHostingAssetValidator() {
+        super(
+                DOMAIN_EMAIL_SUBMISSION_SETUP,
+                AlarmContact.isOptional(),
+
+                NO_EXTRA_PROPERTIES);
+    }
+
+    @Override
+    protected Pattern identifierPattern(final HsHostingAssetEntity assetEntity) {
+        return  Pattern.compile("^" + assetEntity.getParentAsset().getIdentifier() + Pattern.quote(IDENTIFIER_SUFFIX) + "$");
+    }
+
+    @Override
+    public void preprocessEntity(final HsHostingAssetEntity entity) {
+        super.preprocessEntity(entity);
+        if (entity.getIdentifier() == null) {
+            ofNullable(entity.getParentAsset()).ifPresent(pa -> entity.setIdentifier(pa.getIdentifier() + IDENTIFIER_SUFFIX));
+        }
+    }
+}
diff --git a/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetControllerRestTest.java b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetControllerRestTest.java
index 76c5a379..79841ae6 100644
--- a/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetControllerRestTest.java
+++ b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetControllerRestTest.java
@@ -317,6 +317,24 @@ public class HsHostingAssetControllerRestTest {
                             "config": {}
                         }
                     ]
+                """),
+        DOMAIN_EMAIL_MAILBOX_SETUP(
+                List.of(
+                        HsHostingAssetEntity.builder()
+                                .type(HsHostingAssetType.DOMAIN_EMAIL_MAILBOX_SETUP)
+                                .identifier("example.org|MBOX")
+                                .caption("some fake Domain-MBOX-Setup")
+                                .build()),
+                """
+                    [
+                        {
+                            "type": "DOMAIN_EMAIL_MAILBOX_SETUP",
+                            "identifier": "example.org|MBOX",
+                            "caption": "some fake Domain-MBOX-Setup",
+                            "alarmContact": null,
+                            "config": {}
+                        }
+                    ]
                 """);
 
         final HsHostingAssetType assetType;
diff --git a/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEmailMailboxSetupHostingAssetValidatorUnitTest.java b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEmailMailboxSetupHostingAssetValidatorUnitTest.java
new file mode 100644
index 00000000..50d195d9
--- /dev/null
+++ b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsDomainEmailMailboxSetupHostingAssetValidatorUnitTest.java
@@ -0,0 +1,133 @@
+package net.hostsharing.hsadminng.hs.hosting.asset.validators;
+
+import net.hostsharing.hsadminng.hs.booking.item.HsBookingItemEntity;
+import net.hostsharing.hsadminng.hs.booking.item.HsBookingItemType;
+import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetEntity;
+import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetEntity.HsHostingAssetEntityBuilder;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static java.util.Map.entry;
+import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.DOMAIN_EMAIL_MAILBOX_SETUP;
+import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.DOMAIN_SETUP;
+import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.MANAGED_WEBSPACE;
+import static org.assertj.core.api.Assertions.assertThat;
+
+class HsDomainEmailMailboxSetupHostingAssetValidatorUnitTest {
+
+    static final HsHostingAssetEntity validDomainSetupEntity = HsHostingAssetEntity.builder()
+                .type(DOMAIN_SETUP)
+                .identifier("example.org")
+                .build();
+
+    static HsHostingAssetEntityBuilder validEntityBuilder() {
+        return HsHostingAssetEntity.builder()
+                .type(DOMAIN_EMAIL_MAILBOX_SETUP)
+                .parentAsset(validDomainSetupEntity)
+                .assignedToAsset(HsHostingAssetEntity.builder().type(MANAGED_WEBSPACE).build())
+                .identifier("example.org|MBOX");
+    }
+
+    @Test
+    void containsExpectedProperties() {
+        // when
+        final var validator = HostingAssetEntityValidatorRegistry.forType(DOMAIN_EMAIL_MAILBOX_SETUP);
+
+        // then
+        assertThat(validator.properties()).map(Map::toString).isEmpty();
+    }
+
+    @Test
+    void preprocessesTakesIdentifierFromParent() {
+        // given
+        final var givenEntity = validEntityBuilder().build();
+        assertThat(givenEntity.getParentAsset().getIdentifier()).as("precondition failed").isEqualTo("example.org");
+        final var validator = HostingAssetEntityValidatorRegistry.forType(givenEntity.getType());
+
+        // when
+        validator.preprocessEntity(givenEntity);
+
+        // then
+        assertThat(givenEntity.getIdentifier()).isEqualTo("example.org|MBOX");
+    }
+
+    @Test
+    void rejectsInvalidIdentifier() {
+        // given
+        final var givenEntity = validEntityBuilder().identifier("example.org").build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(givenEntity.getType());
+
+        // when
+        final var result = validator.validateEntity(givenEntity);
+
+        // then
+        assertThat(result).containsExactly(
+                "'identifier' expected to match '^example.org\\Q|MBOX\\E$', but is 'example.org'"
+        );
+    }
+
+    @Test
+    void acceptsValidIdentifier() {
+        // given
+        final var givenEntity = validEntityBuilder().identifier(validDomainSetupEntity.getIdentifier()+"|MBOX").build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(givenEntity.getType());
+
+        // when
+        final var result = validator.validateEntity(givenEntity);
+
+        // then
+        assertThat(result).isEmpty();
+    }
+
+    @Test
+    void rejectsInvalidReferencedEntities() {
+        // given
+        final var mangedServerHostingAssetEntity = validEntityBuilder()
+                .bookingItem(HsBookingItemEntity.builder().type(HsBookingItemType.CLOUD_SERVER).build())
+                .parentAsset(HsHostingAssetEntity.builder().type(MANAGED_WEBSPACE).build())
+                .assignedToAsset(null)
+                .build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(mangedServerHostingAssetEntity.getType());
+
+        // when
+        final var result = validator.validateEntity(mangedServerHostingAssetEntity);
+
+        // then
+        assertThat(result).containsExactlyInAnyOrder(
+                "'DOMAIN_EMAIL_MAILBOX_SETUP:example.org|MBOX.bookingItem' must be null but is of type CLOUD_SERVER",
+                "'DOMAIN_EMAIL_MAILBOX_SETUP:example.org|MBOX.parentAsset' must be of type DOMAIN_SETUP but is of type MANAGED_WEBSPACE",
+                "'DOMAIN_EMAIL_MAILBOX_SETUP:example.org|MBOX.assignedToAsset' must be of type MANAGED_WEBSPACE but is null");
+    }
+
+    @Test
+    void acceptsValidEntity() {
+        // given
+        final var givenEntity = validEntityBuilder().build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(givenEntity.getType());
+
+        // when
+        final var errors = validator.validateEntity(givenEntity);
+
+        // then
+        assertThat(errors).isEmpty();
+    }
+
+    @Test
+    void rejectsInvalidProperties() {
+        // given
+        final var mangedServerHostingAssetEntity = validEntityBuilder()
+                .config(Map.ofEntries(
+                        entry("any", "false")
+                ))
+                .build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(mangedServerHostingAssetEntity.getType());
+
+        // when
+        final var result = validator.validateEntity(mangedServerHostingAssetEntity);
+
+        // then
+        assertThat(result).containsExactlyInAnyOrder(
+                "'DOMAIN_EMAIL_MAILBOX_SETUP:example.org|MBOX.config.any' is not expected but is set to 'false'");
+    }
+}