diff --git a/src/backend/core/api/client/viewsets.py b/src/backend/core/api/client/viewsets.py
index 3626f7e..fa2f4a6 100644
--- a/src/backend/core/api/client/viewsets.py
+++ b/src/backend/core/api/client/viewsets.py
@@ -7,6 +7,7 @@ from functools import reduce
 from django.conf import settings
 from django.db.models import OuterRef, Q, Subquery, Value
 from django.db.models.functions import Coalesce
+from django.utils import timezone
 from django.utils.decorators import method_decorator
 from django.views.decorators.cache import cache_page
 
@@ -605,7 +606,7 @@ class StatView(views.APIView):
         context = {
             "total_users": models.User.objects.count(),
             "mau": models.User.objects.filter(
-                last_login__gte=datetime.datetime.now() - datetime.timedelta(30)
+                last_login__gte=timezone.now() - datetime.timedelta(30)
             ).count(),
             "teams": models.Team.objects.count(),
             "domains": domains_models.MailDomain.objects.count(),
diff --git a/src/backend/core/factories.py b/src/backend/core/factories.py
index d92f37a..90fa14c 100644
--- a/src/backend/core/factories.py
+++ b/src/backend/core/factories.py
@@ -240,7 +240,7 @@ class TeamWebhookFactory(factory.django.DjangoModelFactory):
         model = models.TeamWebhook
 
     team = factory.SubFactory(TeamFactory)
-    url = factory.Sequence(lambda n: f"https://example.com/Groups/{n!s}")
+    url = factory.Sequence(lambda n: f"https://nosuchdomain.xyz/Groups/{n!s}")
 
 
 class InvitationFactory(factory.django.DjangoModelFactory):
diff --git a/src/backend/mailbox_manager/admin.py b/src/backend/mailbox_manager/admin.py
index 45cd4cc..1c42350 100644
--- a/src/backend/mailbox_manager/admin.py
+++ b/src/backend/mailbox_manager/admin.py
@@ -1,7 +1,7 @@
 """Admin classes and registrations for People's mailbox manager app."""
 
 from django.contrib import admin, messages
-from django.utils.html import format_html
+from django.utils.html import format_html_join, mark_safe
 from django.utils.translation import gettext_lazy as _
 
 from requests import exceptions
@@ -9,6 +9,9 @@ from requests import exceptions
 from mailbox_manager import enums, models
 from mailbox_manager.utils.dimail import DimailAPIClient
 
+# Prevent Ruff complaining about mark_safe below
+# ruff: noqa: S308
+
 
 @admin.action(description=_("Synchronise from dimail"))
 def sync_mailboxes_from_dimail(modeladmin, request, queryset):  # pylint: disable=unused-argument
@@ -79,10 +82,16 @@ def fetch_domain_status_from_dimail(modeladmin, request, queryset):  # pylint: d
             if domains_updated
             else _("No domain updated."),
         ]
-        messages.success(request, format_html("<br> ".join(map(str, msg_success))))
+        messages.success(
+            request,
+            format_html_join(mark_safe("<br> "), "{}", ([str(m)] for m in msg_success)),
+        )
     if msg_error:
         msg_error.insert(0, _("Check domain failed for:"))
-        messages.error(request, format_html("<br> ".join(map(str, msg_error))))
+        messages.error(
+            request,
+            format_html_join(mark_safe("<br> "), "{}", ([str(m)] for m in msg_error)),
+        )
     if excluded_domains:
         messages.warning(
             request,
diff --git a/src/backend/mailbox_manager/management/commands/setup_dimail_db.py b/src/backend/mailbox_manager/management/commands/setup_dimail_db.py
index 3118c22..40d4bce 100644
--- a/src/backend/mailbox_manager/management/commands/setup_dimail_db.py
+++ b/src/backend/mailbox_manager/management/commands/setup_dimail_db.py
@@ -48,7 +48,7 @@ class Command(BaseCommand):
         # protected behind admin rights but dimail allows to create a first user
         # when database is empty
         self.create_user(
-            auth=(None, None),
+            auth=("", ""),
             name=admin["username"],
             password=admin["password"],
             perms=[],
diff --git a/src/backend/pyproject.toml b/src/backend/pyproject.toml
index de20cc8..ec78b17 100644
--- a/src/backend/pyproject.toml
+++ b/src/backend/pyproject.toml
@@ -140,6 +140,12 @@ python_files = [
     "test_*.py",
     "tests.py",
 ]
+filterwarnings = [
+    # This one can be removed when upgrading to Django 6.0
+    'ignore:The FORMS_URLFIELD_ASSUME_HTTPS transitional setting is deprecated.',
+    # This one can be removed after upgrading DRF to 3.16
+    "ignore:Converter 'drf_format_suffix'"
+]
 
 [tool.coverage.run]
 branch = true