2 files changed, 29 insertions, 2 deletions

diff --git a/src/mailman/rest/addresses.py b/src/mailman/rest/addresses.py
index 9dbbf3fc8..c62048b6a 100644
--- a/src/mailman/rest/addresses.py
+++ b/src/mailman/rest/addresses.py
@@ -211,7 +211,15 @@ class UserAddresses(_AddressBase):
         except InvalidEmailAddressError:
             bad_request(response, b'Invalid email address')
         except ExistingAddressError:
-            bad_request(response, b'Address already exists')
+            # Check if the address is not linked to any user, link it to
+            # the current user and return it.
+            address = user_manager.get_address(**validator(request))
+            if address.user is None:
+                address.user = self._user
+                location = self.path_to('addresses/{0}'.format(address.email))
+                created(response, location)
+            else:
+                bad_request(response, 'Address belongs to other user.')
         else:
             # Link the address to the current user and return it.
             address.user = self._user
diff --git a/src/mailman/rest/tests/test_addresses.py b/src/mailman/rest/tests/test_addresses.py
index d03dc79d7..02c190c08 100644
--- a/src/mailman/rest/tests/test_addresses.py
+++ b/src/mailman/rest/tests/test_addresses.py
@@ -168,7 +168,26 @@ class TestAddresses(unittest.TestCase):
                      'email': 'anne@example.com',
                      })
         self.assertEqual(cm.exception.code, 400)
-        self.assertEqual(cm.exception.reason, b'Address already exists')
+        self.assertEqual(cm.exception.reason, b'Address belongs to other user.')
+
+    def test_add_unlinked_address_to_user(self):
+        user_manager = getUtility(IUserManager)
+        with transaction():
+            anne = user_manager.create_user('anne.person@example.com')
+            user_manager.create_address('anne@example.com')
+        response, content = call_api(
+            'http://localhost:9001/3.0/users/anne.person@example.com/addresses',
+            { 'email': 'anne@example.com'})
+
+        self.assertIn('anne@example.com',
+                      [addr.email for addr in anne.addresses])
+        self.assertEqual(content['status'], '201')
+        self.assertEqual(
+            content['location'],
+            'http://localhost:9001/3.0/addresses/anne@example.com')
+        # The address has no display name.
+        anne_person = user_manager.get_address('anne@example.com')
+        self.assertEqual(anne_person.display_name, '')
 
     def test_invalid_address_bad_request(self):
         # Trying to add an invalid address string returns 400.