diff --git a/modoboa/core/checks.py b/modoboa/core/checks.py
index fb445a9e7..cf601a442 100644
--- a/modoboa/core/checks.py
+++ b/modoboa/core/checks.py
@@ -1,9 +1,18 @@
-from django.core.checks import register, Info, Warning
+from django.core.checks import register, Error, Info, Warning
 from django.conf import settings
 from django.utils.translation import gettext as _
 
 from modoboa.core.utils import generate_rsa_private_key
+from modoboa.parameters.tools import get_global_parameter
+from modoboa.core.password_hashers import get_password_hasher
 
+EOO1 = Error(
+    _("The password scheme you use is not available anymore."),
+    hint=_(
+        "The password scheme you were using has been removed, please upgrade to a stronger one"
+    ),
+    id="modoboa.EOO1",
+)
 
 W001 = Warning(
     _(
@@ -14,6 +23,11 @@ W001 = Warning(
     hint=_("Set `USE_TZ = True` in settings.py"),
     id="modoboa.W001",
 )
+W002 = Warning(
+    _("The password scheme you are using is deprecated."),
+    hint=_("Upgrade your password scheme to a stronger one"),
+    id="modoboa.W002",
+)
 
 
 @register(deploy=True)
@@ -38,3 +52,15 @@ def check_rsa_private_key_exists(app_configs, **kwargs):
     if generate_rsa_private_key(settings.BASE_DIR):
         msgs.append(Info("An RSA private key has been generated for OIDC."))
     return msgs
+
+
+@register()
+def check_password_hasher(app_configs, **kwargs):
+    msgs = []
+    scheme_in_use = get_global_parameter("password_scheme", app="core")
+    hasher = get_password_hasher(scheme_in_use)
+    if not hasher.available:
+        msgs.append(EOO1)
+    elif hasher.deprecated:
+        msgs.append(W002)
+    return msgs
diff --git a/modoboa/core/models.py b/modoboa/core/models.py
index 25d3d4e0f..b947d8bce 100644
--- a/modoboa/core/models.py
+++ b/modoboa/core/models.py
@@ -2,6 +2,7 @@
 
 import re
 from email.header import Header
+from typing import Optional
 
 from django.core.serializers.json import DjangoJSONEncoder
 from django.conf import settings
@@ -96,7 +97,7 @@ class User(AbstractUser):
         super().__init__(*args, **kwargs)
         self.parameters = param_tools.Manager("user", self._parameters)
 
-    def _crypt_password(self, raw_value):
+    def _crypt_password(self, raw_value: str) -> str:
         """Crypt the local password using the appropriate scheme.
 
         In case we don't find the scheme (for example when the
@@ -115,9 +116,17 @@ class User(AbstractUser):
                 "password_scheme", raise_exception=False
             )
         raw_value = smart_bytes(raw_value)
-        return get_password_hasher(scheme.upper())().encrypt(raw_value)
+        hasher = get_password_hasher(scheme.upper())()
+        if not hasher.available:
+            raise InternalError(
+                _(
+                    "The configured password scheme (%s) is not available anymore. Please update your configuration"
+                )
+                % (scheme)
+            )
+        return hasher.encrypt(raw_value)
 
-    def set_password(self, raw_value, curvalue=None):
+    def set_password(self, raw_value: str, curvalue: Optional[str] = None) -> None:
         """Password update.
 
         Update the current mailbox's password with the given clear
diff --git a/modoboa/core/password_hashers/__init__.py b/modoboa/core/password_hashers/__init__.py
index 5bc8bd086..560c43ef4 100644
--- a/modoboa/core/password_hashers/__init__.py
+++ b/modoboa/core/password_hashers/__init__.py
@@ -19,7 +19,7 @@ from modoboa.core.password_hashers.base import (  # NOQA:F401
 )
 
 
-def get_password_hasher(scheme):
+def get_password_hasher(scheme: str) -> PasswordHasher:
     """Retrieve the hasher corresponding to :keyword:`scheme`.
 
     If no class is found, `PLAINHasher` is returned.
diff --git a/modoboa/core/password_hashers/base.py b/modoboa/core/password_hashers/base.py
index 0d355ac63..e56f2ba2e 100644
--- a/modoboa/core/password_hashers/base.py
+++ b/modoboa/core/password_hashers/base.py
@@ -5,10 +5,15 @@ Contains weak hashers (the original ones) available with Modoboa.
 """
 
 import base64
-import crypt
+
+try:
+    import crypt
+except ImportError:
+    crypt = None
 import hashlib
-import string
 from random import Random
+import string
+from typing import Optional
 
 from django.utils.crypto import constant_time_compare
 from django.utils.encoding import force_bytes, force_str
@@ -28,7 +33,15 @@ class MetaHasher(type):
     @property
     def label(cls):
         """Returns the label of the hasher"""
-        return cls.name if not cls._weak else "{} (weak)".format(cls.name)
+        result = cls.name
+        tags = []
+        if cls._weak:
+            tags.append("weak")
+        if cls.deprecated:
+            tags.append("deprecated")
+        if tags:
+            result += f" ({', '.join(tags)})"
+        return result
 
 
 class PasswordHasher(metaclass=MetaHasher):
@@ -36,12 +49,14 @@ class PasswordHasher(metaclass=MetaHasher):
     Base class of all hashers.
     """
 
-    _weak = False
+    _weak: bool = False
+    deprecated: bool = False
+    scheme: str
 
     def __init__(self, target="local"):
         self._target = target
 
-    def _encrypt(self, clearvalue, salt=None):
+    def _encrypt(self, clearvalue: str, salt: Optional[str] = None) -> str:
         raise NotImplementedError
 
     def _b64encode(self, pwhash):
@@ -54,7 +69,11 @@ class PasswordHasher(metaclass=MetaHasher):
             return base64.b64encode(pwhash)
         return pwhash
 
-    def encrypt(self, clearvalue):
+    @property
+    def available(self) -> bool:
+        return True
+
+    def encrypt(self, clearvalue: str) -> str:
         """Encrypt a password.
 
         The format used to store passwords is the same than dovecot's one::
@@ -94,7 +113,7 @@ class PasswordHasher(metaclass=MetaHasher):
     @classmethod
     def get_password_hashers(cls):
         """Return all the PasswordHasher supported by Modoboa"""
-        return cls.__subclasses__()
+        return [hasher for hasher in cls.__subclasses__() if hasher().available]
 
 
 class PLAINHasher(PasswordHasher):
@@ -120,12 +139,17 @@ class CRYPTHasher(PasswordHasher):
     """
 
     _weak = True
+    deprecated = True
+
+    @property
+    def available(self) -> bool:
+        return crypt is not None
 
     @property
     def scheme(self):
         return "{CRYPT}"
 
-    def _encrypt(self, clearvalue, salt=None):
+    def _encrypt(self, clearvalue: str, salt: Optional[str] = None) -> str:
         if salt is None:
             salt = "".join(Random().sample(string.ascii_letters + string.digits, 2))
         return crypt.crypt(clearvalue, salt)
diff --git a/modoboa/core/tests/test_authentication.py b/modoboa/core/tests/test_authentication.py
index 9b0e4e306..7901fe37b 100644
--- a/modoboa/core/tests/test_authentication.py
+++ b/modoboa/core/tests/test_authentication.py
@@ -16,6 +16,7 @@ except ImportError:
 from modoboa.core import constants
 from modoboa.core.password_hashers import get_password_hasher
 from modoboa.core.password_hashers.utils import get_dovecot_schemes
+from modoboa.lib.exceptions import InternalError
 from modoboa.lib.tests import NO_SMTP, ModoTestCase
 from .. import factories, models
 
@@ -252,6 +253,18 @@ class AuthenticationTestCase(ModoTestCase):
         supported_schemes = get_dovecot_schemes()[0]
         self.assertEqual(supported_schemes, ["{MD5-CRYPT}", "{PLAIN}"])
 
+    def test_unavailable_password_scheme(self):
+        self.set_global_parameter("password_scheme", "crypt")
+        hasher = get_password_hasher("crypt")
+        self.assertEqual(hasher.label, "crypt (weak, deprecated)")
+        if hasher().available:
+            return
+        username = "user@test.com"
+        password = "toto"
+        user = models.User.objects.get(username=username)
+        with self.assertRaises(InternalError):
+            user.set_password(password)
+
     def test_fido_auth_begin(self):
         url = reverse("core:fido_auth_begin")
         resp = self.client.post(url)
diff --git a/modoboa/core/tests/test_checks.py b/modoboa/core/tests/test_checks.py
index b3beda5dd..dab27949b 100644
--- a/modoboa/core/tests/test_checks.py
+++ b/modoboa/core/tests/test_checks.py
@@ -2,13 +2,14 @@ import os
 import shutil
 import tempfile
 
-from django.test import SimpleTestCase
 from django.test.utils import override_settings
 
 from modoboa.core import checks
+from modoboa.lib.tests import SimpleModoTestCase
+from modoboa.core.password_scheme.base import CRYPTHasher
 
 
-class CheckSessionCookieSecureTest(SimpleTestCase):
+class CheckSessionCookieSecureTest(SimpleModoTestCase):
 
     def setUp(self):
         self.workdir = tempfile.mkdtemp()
@@ -35,3 +36,11 @@ class CheckSessionCookieSecureTest(SimpleTestCase):
             os.environ["OIDC_RSA_PRIVATE_KEY"] = "KEY"
             msgs = checks.check_rsa_private_key_exists(None)
             self.assertEqual(len(msgs), 0)
+
+    def test_password_hasher_checks(self):
+        self.set_global_parameter("password_scheme", "crypt")
+        msgs = checks.check_password_hasher(None)
+        if CRYPTHasher().available:
+            self.assertEqual(msgs, [checks.W002])
+        else:
+            self.assertEqual(msgs, [checks.E001])
diff --git a/modoboa/lib/tests/__init__.py b/modoboa/lib/tests/__init__.py
index 1c5322920..23425ef51 100644
--- a/modoboa/lib/tests/__init__.py
+++ b/modoboa/lib/tests/__init__.py
@@ -30,7 +30,7 @@ except ImportError:
     NO_LDAP = True
 
 
-class ParametersMixin(object):
+class ParametersMixin:
     """Add tools to manage parameters."""
 
     @classmethod