diff --git a/promgen/admin.py b/promgen/admin.py
index fde2f0bb..06f20bd9 100644
--- a/promgen/admin.py
+++ b/promgen/admin.py
@@ -7,14 +7,12 @@
 from django.contrib import admin
 from django.contrib.auth.admin import UserAdmin
 from django.contrib.auth.models import User
-from django.core import validators
 from django.urls import path
 from django.utils.html import format_html
 from knox.admin import AuthTokenAdmin
 
 from promgen import actions, models, plugins, views
 from promgen.forms import PromgenAuthTokenCreateForm
-from promgen.notification.email import NotificationEmail
 
 
 class PrometheusInline(admin.TabularInline):
@@ -65,11 +63,6 @@ class Meta:
         model = models.Sender
         exclude = ["content_object"]
 
-    def clean(self):
-        if self.cleaned_data["sender"] == NotificationEmail.__module__:
-            validator = validators.EmailValidator()
-            validator(self.cleaned_data["value"])
-
 
 @admin.register(models.Sender)
 class SenderAdmin(admin.ModelAdmin):
diff --git a/promgen/models.py b/promgen/models.py
index 35160710..aa117220 100644
--- a/promgen/models.py
+++ b/promgen/models.py
@@ -11,6 +11,7 @@
 from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import FieldDoesNotExist
+from django.core.validators import EmailValidator
 from django.db import models, transaction
 from django.forms.models import model_to_dict
 from django.urls import reverse
@@ -178,6 +179,20 @@ def filtered(self, alert):
     def get_absolute_url(self):
         return reverse("notifier-edit", kwargs={"pk": self.pk})
 
+    def clean(self):
+        super().clean()
+        if self.sender == "promgen.notification.email":
+            validator = EmailValidator()
+            validator(self.value)
+
+    def save(self, *args, **kwargs):
+        # Django model validation is not automatically invoked when calling the original method
+        # save(). It runs automatically when data is handled through standard Django Forms or
+        # ModelForms. Therefore, we need to explicitly call full_clean() before saving the model
+        # instance to ensure that all field validations are always performed.
+        self.full_clean()
+        super().save(*args, **kwargs)
+
 
 class Filter(models.Model):
     sender = models.ForeignKey("Sender", on_delete=models.CASCADE)
diff --git a/promgen/rest_v2.py b/promgen/rest_v2.py
index cdf8b3e4..d764e51b 100644
--- a/promgen/rest_v2.py
+++ b/promgen/rest_v2.py
@@ -23,6 +23,7 @@
 from rest_framework.exceptions import MethodNotAllowed, NotFound, PermissionDenied, ValidationError
 from rest_framework.renderers import TemplateHTMLRenderer
 from rest_framework.response import Response
+from rest_framework.serializers import as_serializer_error
 from rest_framework.views import APIView, exception_handler
 
 import promgen.templatetags.promgen as promgen_templatetags
@@ -78,6 +79,10 @@ def get_urls(self):
 
 
 def custom_exception_handler(exc, context):
+    if isinstance(exc, DjangoValidationError):
+        # Convert DjangoValidationError to a DRFValidationError
+        exc = ValidationError(detail=as_serializer_error(exc))
+
     # Call REST framework's default exception handler first,
     # to get the standard error response.
     response = exception_handler(exc, context)
diff --git a/promgen/tests/test_rest.py b/promgen/tests/test_rest.py
index aa5f5b6a..cf39b2e9 100644
--- a/promgen/tests/test_rest.py
+++ b/promgen/tests/test_rest.py
@@ -662,14 +662,3 @@ def test_exception_handler(self):
         )
         self.assertEqual(response.status_code, 400)
         self.assertEqual(response.json(), {"name": ["This field may not be blank."]})
-
-        # Unexpected exception (django.ValidationError) returns 500 HTTP code with
-        # the default response.
-        response = self.client.patch(
-            reverse("api-v2:rule-detail", kwargs={"id": 1}),
-            data={"clause": "This clause is not valid."},
-            content_type="application/json",
-            HTTP_AUTHORIZATION=f"Token {admin_token}",
-        )
-        self.assertEqual(response.status_code, 500)
-        self.assertEqual(response.json(), {"error": "Server Error (500)"})