diff --git a/aleksis/apps/postbuero/migrations/0001_initial.py b/aleksis/apps/postbuero/migrations/0001_initial.py
index e5c8659b29b5d1454c0825da459d11038b182b2b..6735ef507b87d081db4adb6015deb75d8157c61c 100644
--- a/aleksis/apps/postbuero/migrations/0001_initial.py
+++ b/aleksis/apps/postbuero/migrations/0001_initial.py
@@ -1,9 +1,10 @@
 # Generated by Django 3.2.11 on 2022-01-19 21:25
 
-import django.contrib.sites.managers
 from django.db import migrations, models
 import django.db.models.deletion
 
+import aleksis.core.managers
+
 
 class Migration(migrations.Migration):
 
@@ -30,7 +31,7 @@ class Migration(migrations.Migration):
                 'verbose_name_plural': 'Mail addresses',
             },
             managers=[
-                ('objects', django.contrib.sites.managers.CurrentSiteManager()),
+                ('objects', aleksis.core.managers.AlekSISBaseManager()),
             ],
         ),
         migrations.AddConstraint(
diff --git a/aleksis/apps/postbuero/migrations/0002_maildomain.py b/aleksis/apps/postbuero/migrations/0002_maildomain.py
index 0025a7e971697373dc269c2189e92fc1c2fa4341..61c96ced6891c7e8bb560b2b28a497f9bfd128d5 100644
--- a/aleksis/apps/postbuero/migrations/0002_maildomain.py
+++ b/aleksis/apps/postbuero/migrations/0002_maildomain.py
@@ -1,9 +1,10 @@
 # Generated by Django 3.2.12 on 2022-02-01 18:47
 
-import django.contrib.sites.managers
 from django.db import migrations, models
 import django.db.models.deletion
 
+import aleksis.core.managers
+
 
 class Migration(migrations.Migration):
 
@@ -27,7 +28,7 @@ class Migration(migrations.Migration):
                 'abstract': False,
             },
             managers=[
-                ('objects', django.contrib.sites.managers.CurrentSiteManager()),
+                ('objects', aleksis.core.managers.AlekSISBaseManager()),
             ],
         ),
         migrations.AlterField(
diff --git a/aleksis/apps/postbuero/migrations/0006_alter_mailaddress_managers_alter_mailalias_managers_and_more.py b/aleksis/apps/postbuero/migrations/0006_alter_mailaddress_managers_alter_mailalias_managers_and_more.py
new file mode 100644
index 0000000000000000000000000000000000000000..8bd28d63e9a503e8019166601d2f397da9e66969
--- /dev/null
+++ b/aleksis/apps/postbuero/migrations/0006_alter_mailaddress_managers_alter_mailalias_managers_and_more.py
@@ -0,0 +1,32 @@
+# Generated by Django 4.2.3 on 2023-07-22 11:05
+
+import aleksis.core.managers
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contenttypes', '0002_remove_content_type_name'),
+        ('sites', '0002_alter_domain_unique'),
+        ('postbuero', '0005_group_address'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='mailaddress',
+            name='managed_by_app_label',
+            field=models.CharField(blank=True, editable=False, max_length=255, verbose_name='App label of app responsible for managing this instance'),
+        ),
+        migrations.AddField(
+            model_name='mailalias',
+            name='managed_by_app_label',
+            field=models.CharField(blank=True, editable=False, max_length=255, verbose_name='App label of app responsible for managing this instance'),
+        ),
+        migrations.AddField(
+            model_name='maildomain',
+            name='managed_by_app_label',
+            field=models.CharField(blank=True, editable=False, max_length=255, verbose_name='App label of app responsible for managing this instance'),
+        ),
+    ]
diff --git a/aleksis/apps/postbuero/schema.py b/aleksis/apps/postbuero/schema.py
index 11ea7ad38269633da87e9e5341f77279154593c7..d58d8412451b8602f793060a2103dc743557dd61 100644
--- a/aleksis/apps/postbuero/schema.py
+++ b/aleksis/apps/postbuero/schema.py
@@ -37,6 +37,7 @@ class MailAddressCreateMutation(DjangoCreateMutation):
     class Meta:
         model = MailAddress
         permissions = ("postbuero.create_mailaddress",)
+        exclude_fields = ("managed_by_app_label",)
 
     @classmethod
     def before_save(cls, root, info, input, obj):  # noqa
@@ -89,6 +90,7 @@ class MailDomainCreateMutation(DjangoCreateMutation):
     class Meta:
         model = MailDomain
         permissions = ("postbuero.create_maildomain",)
+        exclude_fields = ("managed_by_app_label",)
 
 
 class MailDomainDeleteMutation(DeleteMutation):
@@ -99,7 +101,7 @@ class MailDomainDeleteMutation(DeleteMutation):
 class MailDomainBatchPatchMutation(PermissionBatchPatchMixin, DjangoBatchPatchMutation):
     class Meta:
         model = MailDomain
-        permissions = "postbuero.change_maildomain"
+        permissions = ("postbuero.change_maildomain",)
 
 
 class Query(graphene.ObjectType):
diff --git a/pyproject.toml b/pyproject.toml
index 83cc1a497b942f47419cf391bc14d07c0a6eed8d..45c6d15a086c0a83fcc4343decca0a280379d726 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "AlekSIS-App-Postbuero"
-version = "2.0b0"
+version = "3.0.dev0"
 packages = [
     { include = "aleksis" }
 ]
@@ -25,7 +25,7 @@ secondary = true
 
 [tool.poetry.dependencies]
 python = "^3.9"
-AlekSIS-Core = "^3.0b0"
+AlekSIS-Core = "^4.0.0.dev0"
 
 [tool.poetry.dev-dependencies]
 aleksis-builddeps = "*"