diff --git a/zerver/tests/test_auth_backends.py b/zerver/tests/test_auth_backends.py
index 134d7b59d7..d242db232d 100644
--- a/zerver/tests/test_auth_backends.py
+++ b/zerver/tests/test_auth_backends.py
@@ -57,7 +57,7 @@ from zproject.backends import ZulipDummyBackend, EmailAuthBackend, \
     ZulipLDAPUserPopulator, DevAuthBackend, GitHubAuthBackend, ZulipAuthMixin, \
     dev_auth_enabled, password_auth_enabled, github_auth_enabled, \
     require_email_format_usernames, AUTH_BACKEND_NAME_MAP, \
-    ZulipLDAPConfigurationError
+    ZulipLDAPConfigurationError, ZulipLDAPExceptionOutsideDomain
 
 from zerver.views.auth import (maybe_send_to_registration,
                                login_or_register_remote_user,
@@ -2177,6 +2177,23 @@ class TestLDAP(ZulipTestCase):
             assert(user_profile is not None)
             self.assertEqual(user_profile.email, self.example_email("hamlet"))
 
+    @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
+    def test_login_success_with_username(self) -> None:
+        self.mock_ldap.directory = {
+            'uid=hamlet,ou=users,dc=zulip,dc=com': {
+                'userPassword': 'testing'
+            }
+        }
+        with self.settings(
+                LDAP_APPEND_DOMAIN='zulip.com',
+                AUTH_LDAP_BIND_PASSWORD='',
+                AUTH_LDAP_USER_DN_TEMPLATE='uid=%(user)s,ou=users,dc=zulip,dc=com'):
+            user_profile = self.backend.authenticate("hamlet", 'testing',
+                                                     realm=get_realm('zulip'))
+
+            assert(user_profile is not None)
+            self.assertEqual(user_profile.email, self.example_email("hamlet"))
+
     @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
     def test_login_success_with_email_attr(self) -> None:
         self.mock_ldap.directory = {
@@ -2231,12 +2248,28 @@ class TestLDAP(ZulipTestCase):
         self.assertTrue(backend.get_group_permissions(None, None) == set())
 
     @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
-    def test_django_to_ldap_username(self) -> None:
+    def test_django_to_ldap_username_without_append_domain(self) -> None:
+        backend = self.backend
+        username = backend.django_to_ldap_username('"hamlet@test"@zulip.com')
+        self.assertEqual(username, '"hamlet@test"@zulip.com')
+
+    @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
+    def test_django_to_ldap_username_with_append_domain(self) -> None:
         backend = self.backend
         with self.settings(LDAP_APPEND_DOMAIN='zulip.com'):
             username = backend.django_to_ldap_username('"hamlet@test"@zulip.com')
             self.assertEqual(username, '"hamlet@test"')
 
+            username = backend.django_to_ldap_username('"hamlet@test"@zulip')
+            self.assertEqual(username, '"hamlet@test"@zulip')
+
+    @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
+    def test_django_to_ldap_username_with_invalid_domain(self) -> None:
+        backend = self.backend
+        with self.settings(LDAP_APPEND_DOMAIN='zulip.com'), \
+                self.assertRaises(ZulipLDAPExceptionOutsideDomain):
+            backend.django_to_ldap_username('"hamlet@test"@test.com')
+
     @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
     def test_ldap_to_django_username(self) -> None:
         backend = self.backend
diff --git a/zproject/backends.py b/zproject/backends.py
index 83c30d6f73..999e7016ed 100644
--- a/zproject/backends.py
+++ b/zproject/backends.py
@@ -220,6 +220,13 @@ class ZulipRemoteUserBackend(RemoteUserBackend):
         email = remote_user_to_email(remote_user)
         return common_get_active_user(email, realm, return_data=return_data)
 
+def is_valid_email(email: str) -> bool:
+    try:
+        validate_email(email)
+    except ValidationError:
+        return False
+    return True
+
 def email_belongs_to_ldap(realm: Realm, email: str) -> bool:
     if not ldap_auth_enabled(realm):
         return False
@@ -287,10 +294,11 @@ class ZulipLDAPAuthBackendBase(ZulipAuthMixin, LDAPBackend):
 
     def django_to_ldap_username(self, username: str) -> str:
         if settings.LDAP_APPEND_DOMAIN:
-            if not username.endswith("@" + settings.LDAP_APPEND_DOMAIN):
-                raise ZulipLDAPExceptionOutsideDomain("Email %s does not match LDAP domain %s." % (
-                    username, settings.LDAP_APPEND_DOMAIN))
-            return email_to_username(username)
+            if is_valid_email(username):
+                if not username.endswith("@" + settings.LDAP_APPEND_DOMAIN):
+                    raise ZulipLDAPExceptionOutsideDomain("Email %s does not match LDAP domain %s." % (
+                        username, settings.LDAP_APPEND_DOMAIN))
+                return email_to_username(username)
         return username
 
     def ldap_to_django_username(self, username: str) -> str: