🐛(aliases) alias destination can be devnull@devnull

devnull@devnull is not considered a valid email address by django's
EmailFieldValidator but it's a special address in dimail's config.

Make "destination" a CharField instead of an EmailField to replace
validator and add devnull to allowlist.

CHANGELOG.md

@@ -8,6 +8,10 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Fixed
+
+- 🐛(aliases) authorize special domain devnull in alias destinations #1029 
+
 ## [1.22.1] - 2026-01-21
 
 - 🔒️(organization) the first user is not admin #776

src/backend/mailbox_manager/migrations/0028_alias.py

@@ -19,7 +19,7 @@ class Migration(migrations.Migration):
                 ('created_at', models.DateTimeField(auto_now_add=True, help_text='date and time at which a record was created', verbose_name='created at')),
                 ('updated_at', models.DateTimeField(auto_now=True, help_text='date and time at which a record was last updated', verbose_name='updated at')),
                 ('local_part', models.CharField(max_length=100)),
-                ('destination', models.EmailField(max_length=254, verbose_name='destination address')),
+                ('destination', models.CharField(max_length=254, validators=[django.core.validators.EmailValidator(allowlist=['localhost', 'devnull'])], verbose_name='destination address')),
                 ('domain', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='aliases', to='mailbox_manager.maildomain')),
             ],
             options={

src/backend/mailbox_manager/models.py

@@ -9,6 +9,7 @@ from django.conf import settings
 from django.contrib.auth.base_user import AbstractBaseUser
 from django.contrib.sites.models import Site
 from django.core import exceptions, mail, validators
+from django.core.validators import EmailValidator
 from django.db import models
 from django.db.models.functions import Lower
 from django.template.loader import render_to_string
@@ -460,7 +461,15 @@ class Alias(BaseModel):
     """Model for aliases."""
 
     local_part = models.CharField(max_length=100, blank=False)
-    destination = models.EmailField(_("destination address"), null=False, blank=False)
+    destination = models.CharField(
+        _("destination address"),
+        max_length=254,
+        null=False,
+        blank=False,
+        validators=[
+            EmailValidator(allowlist=["localhost", "devnull"]),
+        ],
+    )
     domain = models.ForeignKey(
         MailDomain,
         on_delete=models.CASCADE,

src/backend/mailbox_manager/tests/api/aliases/test_api_aliases_create.py

@@ -182,3 +182,33 @@ def test_api_aliases_create__existing_mailbox_ok(dimail_token_ok):
     )
     assert response.status_code == status.HTTP_201_CREATED
     assert models.Alias.objects.exists()
+
+
+@responses.activate
+def test_api_aliases_create__devnull_destination_ok(dimail_token_ok):
+    """Can create alias where destination is devnull@devnull."""
+    access = factories.MailDomainAccessFactory(
+        role="owner", domain=factories.MailDomainEnabledFactory()
+    )
+
+    client = APIClient()
+    client.force_login(access.user)
+
+    responses.post(
+        re.compile(rf".*/domains/{access.domain.name}/aliases/"),
+        json={
+            "username": "spammy-address",
+            "domain": access.domain.name,
+            "destination": "devnull@devnull",
+            "allow_to_send": False,
+        },
+        status=status.HTTP_201_CREATED,
+        content_type="application/json",
+    )
+
+    response = client.post(
+        f"/api/v1.0/mail-domains/{access.domain.slug}/aliases/",
+        {"local_part": "spammy-address", "destination": "devnull@devnull"},
+    )
+    assert response.status_code == status.HTTP_201_CREATED
+    assert models.Alias.objects.exists()

src/backend/mailbox_manager/tests/models/test_aliases.py

@@ -0,0 +1,19 @@
+"""
+Unit tests for the Alias model
+"""
+
+import pytest
+
+from mailbox_manager import factories, models
+
+pytestmark = pytest.mark.django_db
+
+
+def test_models_aliases__devnull_destination_ok():
+    """Can create alias where destination is devnull@devnull."""
+
+    models.Alias.objects.create(
+        local_part="spam",
+        domain=factories.MailDomainEnabledFactory(),
+        destination="devnull@devnull",
+    )

src/backend/mailbox_manager/tests/test_utils_dimail_client.py

@@ -199,6 +199,12 @@ def test_dimail_synchronization__synchronize_aliases(dimail_token_ok):  # pylint
             "destination": existing_mailbox.secondary_email,
             "allow_to_send": False,
         },
+        {  # alias to devnull@devnull
+            "username": "spam",
+            "domain": alias.domain.name,
+            "destination": "devnull@devnull",
+            "allow_to_send": False,
+        },
     ]
     responses.get(
         re.compile(rf".*/domains/{alias.domain.name}/aliases/"),
@@ -209,8 +215,8 @@ def test_dimail_synchronization__synchronize_aliases(dimail_token_ok):  # pylint
 
     imported_aliases = dimail_client.import_aliases(alias.domain)
 
-    assert len(imported_aliases) == 3
-    assert models.Alias.objects.count() == 4
+    assert len(imported_aliases) == 4
+    assert models.Alias.objects.count() == 5
 
 
 @pytest.mark.parametrize(