diff --git a/app/celery/nightly_tasks.py b/app/celery/nightly_tasks.py
index 73086fb40..060834550 100644
--- a/app/celery/nightly_tasks.py
+++ b/app/celery/nightly_tasks.py
@@ -258,19 +258,27 @@ def raise_alert_if_letter_notifications_still_sending():
     today = datetime.utcnow().date()
 
     # Do nothing on the weekend
-    if today.isoweekday() in [6, 7]:
+    if today.isoweekday() in {6, 7}:  # sat, sun
         return
 
-    if today.isoweekday() in [1, 2]:
+    if today.isoweekday() in {1, 2}:  # mon, tues. look for files from before the weekend
         offset_days = 4
     else:
         offset_days = 2
-    still_sending = Notification.query.filter(
+
+    q = Notification.query.filter(
         Notification.notification_type == LETTER_TYPE,
         Notification.status == NOTIFICATION_SENDING,
         Notification.key_type == KEY_TYPE_NORMAL,
         func.date(Notification.sent_at) <= today - timedelta(days=offset_days)
-    ).count()
+    )
+
+    if today.isoweekday() in {2, 4}:  # on tue, thu, we only care about first class letters
+        q = q.filter(
+            Notification.postage == 'first'
+        )
+
+    still_sending = q.count()
 
     if still_sending:
         message = "There are {} letters in the 'sending' state from {}".format(
diff --git a/tests/app/celery/test_nightly_tasks.py b/tests/app/celery/test_nightly_tasks.py
index 8eeedbe0b..e1c86c1ba 100644
--- a/tests/app/celery/test_nightly_tasks.py
+++ b/tests/app/celery/test_nightly_tasks.py
@@ -471,8 +471,8 @@ def test_alert_if_letter_notifications_still_sending_does_nothing_on_the_weekend
 def test_monday_alert_if_letter_notifications_still_sending_reports_thursday_letters(sample_letter_template, mocker):
     thursday = datetime(2018, 1, 11, 13, 30)
     yesterday = datetime(2018, 1, 14, 13, 30)
-    create_notification(template=sample_letter_template, status='sending', sent_at=thursday)
-    create_notification(template=sample_letter_template, status='sending', sent_at=yesterday)
+    create_notification(template=sample_letter_template, status='sending', sent_at=thursday, postage='second')
+    create_notification(template=sample_letter_template, status='sending', sent_at=yesterday, postage='second')
 
     mock_create_ticket = mocker.patch("app.celery.nightly_tasks.zendesk_client.create_ticket")
 
@@ -489,8 +489,10 @@ def test_monday_alert_if_letter_notifications_still_sending_reports_thursday_let
 def test_tuesday_alert_if_letter_notifications_still_sending_reports_friday_letters(sample_letter_template, mocker):
     friday = datetime(2018, 1, 12, 13, 30)
     yesterday = datetime(2018, 1, 14, 13, 30)
-    create_notification(template=sample_letter_template, status='sending', sent_at=friday)
-    create_notification(template=sample_letter_template, status='sending', sent_at=yesterday)
+    create_notification(template=sample_letter_template, status='sending', sent_at=friday, postage='first')
+    create_notification(template=sample_letter_template, status='sending', sent_at=yesterday, postage='first')
+    # doesn't get reported because it's second class, and it's tuesday today
+    create_notification(template=sample_letter_template, status='sending', sent_at=friday, postage='second')
 
     mock_create_ticket = mocker.patch("app.celery.nightly_tasks.zendesk_client.create_ticket")