diff --git a/app/main/views/send.py b/app/main/views/send.py
index b1cea53a8..81c62771c 100644
--- a/app/main/views/send.py
+++ b/app/main/views/send.py
@@ -1,4 +1,3 @@
-import itertools
 import time
 import uuid
 from string import ascii_uppercase
@@ -517,19 +516,27 @@ def _check_messages(service_id, template_id, upload_id, preview_row):
         current_service,
         show_recipient=False,
     )
+
+    allow_list = []
+    if current_service.trial_mode:
+        # Adding the simulated numbers to allow list
+        # so they can be sent in trial mode
+        for user in Users(service_id):
+            allow_list.extend([user.name, user.mobile_number, user.email_address])
+        # Failed sms number
+        allow_list.extend(["simulated user", "+14254147167", "simulated@simulated.gov"])
+        # Success sms number
+        allow_list.extend(
+            ["simulated user two", "+14254147755", "simulatedtwo@simulated.gov"]
+        )
+    else:
+        allow_list = None
     recipients = RecipientCSV(
         contents,
         template=template or simplifed_template,
         max_initial_rows_shown=50,
         max_errors_shown=50,
-        guestlist=(
-            itertools.chain.from_iterable(
-                [user.name, user.mobile_number, user.email_address]
-                for user in Users(service_id)
-            )
-            if current_service.trial_mode
-            else None
-        ),
+        guestlist=allow_list,
         remaining_messages=remaining_messages,
         allow_international_sms=current_service.has_permission("international_sms"),
     )
@@ -560,7 +567,9 @@ def _check_messages(service_id, template_id, upload_id, preview_row):
 
     if preview_row < len(recipients) + 2:
         template.values = recipients[preview_row - 2].recipient_and_personalisation
-        simplifed_template.values = recipients[preview_row - 2].recipient_and_personalisation
+        simplifed_template.values = recipients[
+            preview_row - 2
+        ].recipient_and_personalisation
     elif preview_row > 2:
         abort(404)
 
@@ -863,7 +872,7 @@ def _check_notification(service_id, template_id, exception=None):
         back_link_from_preview=back_link_from_preview,
         choose_time_form=choose_time_form,
         **(get_template_error_dict(exception) if exception else {}),
-        simplifed_template=simplifed_template
+        simplifed_template=simplifed_template,
     )
 
 
diff --git a/tests/app/main/views/test_send.py b/tests/app/main/views/test_send.py
index 35309f57f..a33f975ba 100644
--- a/tests/app/main/views/test_send.py
+++ b/tests/app/main/views/test_send.py
@@ -2612,8 +2612,10 @@ def test_preview_notification_shows_preview(
         session["placeholders"] = {}
 
     page = client_request.post(
-        "main.preview_notification", service_id=service_one["id"], template_id=fake_uuid,
-        _expected_status=200
+        "main.preview_notification",
+        service_id=service_one["id"],
+        template_id=fake_uuid,
+        _expected_status=200,
     )
     assert page.h1.text.strip() == "Preview"
     assert (page.find_all("a", {"class": "usa-back-link"})[0]["href"]) == url_for(