diff --git a/app/celery/nightly_tasks.py b/app/celery/nightly_tasks.py
index 03b84f7e7..f4dd5e491 100644
--- a/app/celery/nightly_tasks.py
+++ b/app/celery/nightly_tasks.py
@@ -2,6 +2,9 @@ from datetime import datetime, timedelta
 
 import pytz
 from flask import current_app
+from notifications_utils.clients.zendesk.zendesk_client import (
+    NotifySupportTicket,
+)
 from sqlalchemy import func
 from sqlalchemy.exc import SQLAlchemyError
 
@@ -179,11 +182,15 @@ def raise_alert_if_letter_notifications_still_sending():
         # Only send alerts in production
         if current_app.config['NOTIFY_ENVIRONMENT'] in ['live', 'production', 'test']:
             message += ". Resolve using https://github.com/alphagov/notifications-manuals/wiki/Support-Runbook#deal-with-letters-still-in-sending"  # noqa
-            zendesk_client.create_ticket(
-                subject="[{}] Letters still sending".format(current_app.config['NOTIFY_ENVIRONMENT']),
+
+            ticket = NotifySupportTicket(
+                subject=f"[{current_app.config['NOTIFY_ENVIRONMENT']}] Letters still sending",
                 message=message,
-                ticket_type=zendesk_client.TYPE_INCIDENT
+                ticket_type=NotifySupportTicket.TYPE_INCIDENT,
+                technical_ticket=True,
+                ticket_categories=['notify_letters']
             )
+            zendesk_client.send_ticket_to_zendesk(ticket)
         else:
             current_app.logger.info(message)
 
diff --git a/tests/app/celery/test_nightly_tasks.py b/tests/app/celery/test_nightly_tasks.py
index 07091aff4..6f9a6c288 100644
--- a/tests/app/celery/test_nightly_tasks.py
+++ b/tests/app/celery/test_nightly_tasks.py
@@ -1,11 +1,13 @@
 from datetime import date, datetime, timedelta
-from unittest.mock import call
+from unittest.mock import ANY, call
 
 import pytest
 import pytz
 from flask import current_app
 from freezegun import freeze_time
-from notifications_utils.clients.zendesk.zendesk_client import ZendeskClient
+from notifications_utils.clients.zendesk.zendesk_client import (
+    NotifySupportTicket,
+)
 
 from app.celery import nightly_tasks
 from app.celery.nightly_tasks import (
@@ -232,34 +234,47 @@ def test_should_call_delete_inbound_sms(notify_api, mocker):
     assert nightly_tasks.delete_inbound_sms_older_than_retention.call_count == 1
 
 
-def test_create_ticket_if_letter_notifications_still_sending(mocker):
+def test_create_ticket_if_letter_notifications_still_sending(notify_api, mocker):
     mock_get_letters = mocker.patch(
         "app.celery.nightly_tasks.get_letter_notifications_still_sending_when_they_shouldnt_be"
     )
 
     mock_get_letters.return_value = 1, date(2018, 1, 15)
-    mock_create_ticket = mocker.patch("app.celery.nightly_tasks.zendesk_client.create_ticket")
-
-    raise_alert_if_letter_notifications_still_sending()
-
-    mock_create_ticket.assert_called_once_with(
-        subject="[test] Letters still sending",
-        message="There are 1 letters in the 'sending' state from Monday 15 January. Resolve using https://github.com/alphagov/notifications-manuals/wiki/Support-Runbook#deal-with-letters-still-in-sending",  # noqa
-        ticket_type=ZendeskClient.TYPE_INCIDENT
+    mock_create_ticket = mocker.spy(NotifySupportTicket, '__init__')
+    mock_send_ticket_to_zendesk = mocker.patch(
+        'app.celery.nightly_tasks.zendesk_client.send_ticket_to_zendesk',
+        autospec=True,
     )
 
+    raise_alert_if_letter_notifications_still_sending()
+    mock_create_ticket.assert_called_once_with(
+        ANY,
+        subject='[test] Letters still sending',
+        message=(
+            "There are 1 letters in the 'sending' state from Monday 15 January. Resolve using "
+            "https://github.com/alphagov/notifications-manuals/wiki/Support-Runbook#deal-with-letters-still-in-sending"
+            ),
+        ticket_type='incident',
+        technical_ticket=True,
+        ticket_categories=['notify_letters']
+    )
+    mock_send_ticket_to_zendesk.assert_called_once()
 
-def test_dont_create_ticket_if_letter_notifications_not_still_sending(mocker):
+
+def test_dont_create_ticket_if_letter_notifications_not_still_sending(notify_api, mocker):
     mock_get_letters = mocker.patch(
         "app.celery.nightly_tasks.get_letter_notifications_still_sending_when_they_shouldnt_be"
     )
 
     mock_get_letters.return_value = 0, None
-    mock_create_ticket = mocker.patch("app.celery.nightly_tasks.zendesk_client.create_ticket")
+    mock_send_ticket_to_zendesk = mocker.patch(
+        "app.celery.nightly_tasks.zendesk_client.send_ticket_to_zendesk",
+        autospec=True
+    )
 
     raise_alert_if_letter_notifications_still_sending()
 
-    mock_create_ticket.assert_not_called()
+    mock_send_ticket_to_zendesk.assert_not_called()
 
 
 @freeze_time("Thursday 17th January 2018 17:00")