diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index 58a5b1f4f..93653368a 100644
--- a/modoboa/admin/forms/domain.py
+++ b/modoboa/admin/forms/domain.py
@@ -96,6 +96,14 @@ class DomainFormGeneral(forms.ModelForm, DynamicForm):
                 "name", _("A %s with this name already exists")
                 % unicode(label)
             )
+        condition = (
+            self.cleaned_data["quota"] != 0 and
+            self.cleaned_data["default_mailbox_quota"] >
+            self.cleaned_data["quota"])
+        if condition:
+            self.add_error(
+                "default_mailbox_quota",
+                _("Cannot be greater than domain quota"))
         if self.user.role == "Resellers":
             limit = self.user.userobjectlimit_set.get(name="quota")
             if limit.max_value != 0:
diff --git a/modoboa/admin/models/domain.py b/modoboa/admin/models/domain.py
index 666514796..cfae8f6f3 100644
--- a/modoboa/admin/models/domain.py
+++ b/modoboa/admin/models/domain.py
@@ -265,6 +265,11 @@ class Domain(AdminObject):
                 _("Invalid default mailbox quota value for domain '{}'")
                 .format(self.name)
             )
+        if self.quota != 0 and self.default_mailbox_quota > self.quota:
+            raise BadRequest(
+                _("Default mailbox quota cannot be greater than domain "
+                  "quota")
+            )
         self.enabled = (row[4].strip() in ["True", "1", "yes", "y"])
         core_signals.can_create_object.send(
             sender=self.__class__, context=user, klass=Domain,
diff --git a/modoboa/admin/serializers.py b/modoboa/admin/serializers.py
index 20a4e10fd..5c6aee1b9 100644
--- a/modoboa/admin/serializers.py
+++ b/modoboa/admin/serializers.py
@@ -27,6 +27,17 @@ class DomainSerializer(serializers.ModelSerializer):
             "pk", "name", "quota", "default_mailbox_quota", "enabled", "type",
         )
 
+    def validate(self, data):
+        """Check quota values."""
+        quota = data.get("quota", 0)
+        default_mailbox_quota = data.get("default_mailbox_quota", 0)
+        if quota != 0 and default_mailbox_quota > quota:
+            raise serializers.ValidationError({
+                "default_mailbox_quota":
+                _("Cannot be greater than domain quota")
+            })
+        return data
+
     def create(self, validated_data):
         """Set permissions."""
         domain = models.Domain(**validated_data)
diff --git a/modoboa/admin/tests/test_api.py b/modoboa/admin/tests/test_api.py
index a56eb0161..0d17f9702 100644
--- a/modoboa/admin/tests/test_api.py
+++ b/modoboa/admin/tests/test_api.py
@@ -53,6 +53,12 @@ class DomainAPITestCase(ModoAPITestCase):
         self.assertEqual(response.status_code, 400)
         self.assertIn("name", response.data)
 
+        response = self.client.post(
+            url, {"name": "test5.com", "quota": 1, "default_mailbox_quota": 10}
+        )
+        self.assertEqual(response.status_code, 400)
+        self.assertIn("default_mailbox_quota", response.data)
+
         self.client.credentials(
             HTTP_AUTHORIZATION='Token ' + self.da_token.key)
         response = self.client.post(
diff --git a/modoboa/admin/tests/test_domain.py b/modoboa/admin/tests/test_domain.py
index 859d985d6..5165a5722 100644
--- a/modoboa/admin/tests/test_domain.py
+++ b/modoboa/admin/tests/test_domain.py
@@ -126,6 +126,33 @@ class DomainTestCase(ModoTestCase):
         self.assertTrue(
             self.client.login(username="toto@pouet.com", password=password))
 
+    def test_quota_constraints(self):
+        """Check quota constraints."""
+        values = {
+            "name": "pouet.com", "quota": 10, "default_mailbox_quota": 100,
+            "create_dom_admin": True, "dom_admin_username": "toto",
+            "create_aliases": True, "type": "domain", "stepid": 'step3'
+        }
+        response = self.ajax_post(
+            reverse("admin:domain_add"),
+            values, status=400
+        )
+        self.assertEqual(
+            response["form_errors"]["default_mailbox_quota"][0],
+            "Cannot be greater than domain quota")
+
+        dom = Domain.objects.get(name="test.com")
+        values["name"] = dom.name
+        values["quota"] = 10
+        values["default_mailbox_quota"] = 100
+        response = self.ajax_post(
+            reverse("admin:domain_change", args=[dom.pk]),
+            values, status=400
+        )
+        self.assertEqual(
+            response["form_errors"]["default_mailbox_quota"][0],
+            "Cannot be greater than domain quota")
+
     def test_create_using_default_quota(self):
         """Check that default value is used for creation."""
         self.set_global_parameter("default_domain_quota", 500)
@@ -157,8 +184,7 @@ class DomainTestCase(ModoTestCase):
             dom.alias_set.filter(address="postmaster@pouet.com").exists())
 
     def test_delete(self):
-        """Test the removal of a domain
-        """
+        """Test the removal of a domain."""
         dom = Domain.objects.get(name="test.com")
         self.ajax_post(
             reverse("admin:domain_delete", args=[dom.id]),
diff --git a/modoboa/admin/tests/test_import_.py b/modoboa/admin/tests/test_import_.py
index 067c50cab..73d8aea76 100644
--- a/modoboa/admin/tests/test_import_.py
+++ b/modoboa/admin/tests/test_import_.py
@@ -64,6 +64,12 @@ domainalias; domalias1.com; domain1.com; True
                         name="domains.csv")
         response = self.client.post(url, {"sourcefile": f})
         self.assertContains(response, "Invalid default mailbox quota")
+        f = ContentFile("domain; domain1.com; 10; 100; True",
+                        name="domains.csv")
+        response = self.client.post(url, {"sourcefile": f})
+        self.assertContains(
+            response,
+            "Default mailbox quota cannot be greater than domain quota")
 
     def test_import_domains_with_conflict(self):
         f = ContentFile(b"""domain;test.alias;100;10;True