diff --git a/app/main/views/send.py b/app/main/views/send.py
index 5fa68d173..249be7bd7 100644
--- a/app/main/views/send.py
+++ b/app/main/views/send.py
@@ -1068,7 +1068,7 @@ def send_notification(service_id, template_id):
         noti = notification_api_client.send_notification(
             service_id,
             template_id=db_template['id'],
-            recipient=session['recipient'] or session['placeholders']['address line 1'],
+            recipient=session['recipient'] or Columns(session['placeholders'])['address line 1'],
             personalisation=session['placeholders'],
             sender_id=session['sender_id'] if 'sender_id' in session else None
         )
diff --git a/tests/app/main/views/test_send.py b/tests/app/main/views/test_send.py
index a43a06420..2e10a971d 100644
--- a/tests/app/main/views/test_send.py
+++ b/tests/app/main/views/test_send.py
@@ -3773,6 +3773,29 @@ def test_send_notification_submits_data(
     )
 
 
+@pytest.mark.parametrize('placeholders', (
+    {'address line 1': 'Foo'},
+    {'ADDRESSLINE_1': 'Foo'},
+))
+def test_send_notification_submits_data_for_letter(
+    client_request,
+    fake_uuid,
+    mock_send_notification,
+    mock_get_service_letter_template,
+    placeholders,
+):
+    with client_request.session_transaction() as session:
+        session['recipient'] = None
+        session['placeholders'] = placeholders
+
+    client_request.post(
+        'main.send_notification',
+        service_id=SERVICE_ONE_ID,
+        template_id=fake_uuid
+    )
+    assert mock_send_notification.call_args[1]['recipient'] == 'Foo'
+
+
 def test_send_notification_clears_session(
     client_request,
     service_one,