diff --git a/app/notify_client/user_api_client.py b/app/notify_client/user_api_client.py
index 878ffd67f..c5283ca43 100644
--- a/app/notify_client/user_api_client.py
+++ b/app/notify_client/user_api_client.py
@@ -40,7 +40,7 @@ class UserApiClient(NotifyAdminAPIClient):
         return self.get("/user/{}".format(user_id))
 
     def get_user_by_email(self, email_address):
-        user_data = self.post('/user/email', params={'email': email_address})
+        user_data = self.post('/user/email', data={'email': email_address})
         return user_data['data']
 
     def get_user_by_email_or_none(self, email_address):
diff --git a/tests/app/notify_client/test_user_client.py b/tests/app/notify_client/test_user_client.py
index 264d293f9..f539b159c 100644
--- a/tests/app/notify_client/test_user_client.py
+++ b/tests/app/notify_client/test_user_client.py
@@ -33,14 +33,14 @@ def test_client_gets_all_users_for_service(
 def test_client_uses_correct_find_by_email(mocker, api_user_active):
 
     expected_url = '/user/email'
-    expected_params = {'email': api_user_active['email_address']}
+    expected_data = {'email': api_user_active['email_address']}
 
     user_api_client.max_failed_login_count = 1  # doesn't matter for this test
     mock_post = mocker.patch('app.notify_client.user_api_client.UserApiClient.post')
 
     user_api_client.get_user_by_email(api_user_active['email_address'])
 
-    mock_post.assert_called_once_with(expected_url, params=expected_params)
+    mock_post.assert_called_once_with(expected_url, data=expected_data)
 
 
 def test_client_only_updates_allowed_attributes(mocker):