diff --git a/app/main/views/send.py b/app/main/views/send.py
index 7f5ab7fba..cfab9b585 100644
--- a/app/main/views/send.py
+++ b/app/main/views/send.py
@@ -115,9 +115,16 @@ def send_messages(service_id, template_id):
             session['file_uploads'].keys())
         )
 
-    session['sender_id'] = None
     db_template = service_api_client.get_service_template(service_id, template_id)['data']
 
+    email_reply_to = None
+    sms_sender = None
+
+    if db_template['template_type'] == 'email':
+        email_reply_to = get_email_reply_to_address_from_session()
+    elif db_template['template_type'] == 'sms':
+        sms_sender = get_sms_sender_from_session()
+
     if email_or_sms_not_enabled(db_template['template_type'], current_service.permissions):
         return redirect(url_for(
             '.action_blocked',
@@ -139,6 +146,8 @@ def send_messages(service_id, template_id):
             filetype='png',
             page_count=get_page_count_for_letter(db_template),
         ),
+        email_reply_to=email_reply_to,
+        sms_sender=sms_sender,
     )
 
     form = CsvUploadForm()
@@ -626,17 +635,20 @@ def check_messages(service_id, template_id, upload_id, row_index=2):
 
     data['original_file_name'] = SanitiseASCII.encode(data.get('original_file_name', ''))
 
-    set_metadata_on_csv_upload(
-        service_id,
-        upload_id,
-        notification_count=data['count_of_recipients'],
-        template_id=str(template_id),
-        valid=True,
-        original_file_name=unicode_truncate(
+    metadata_kwargs = {
+        'notification_count': data['count_of_recipients'],
+        'template_id': str(template_id),
+        'valid': True,
+        'original_file_name': unicode_truncate(
             data['original_file_name'],
             1600,
         ),
-    )
+    }
+
+    if session.get('sender_id'):
+        metadata_kwargs['sender_id'] = session['sender_id']
+
+    set_metadata_on_csv_upload(service_id, upload_id, **metadata_kwargs)
 
     return render_template('views/check/ok.html', **data)
 
@@ -696,6 +708,8 @@ def start_job(service_id, upload_id):
         scheduled_for=request.form.get('scheduled_for', '')
     )
 
+    session.pop('sender_id', None)
+
     return redirect(
         url_for(
             'main.view_job',
diff --git a/tests/app/main/views/test_send.py b/tests/app/main/views/test_send.py
index be9fef204..3325501c4 100644
--- a/tests/app/main/views/test_send.py
+++ b/tests/app/main/views/test_send.py
@@ -2659,6 +2659,48 @@ def test_check_messages_column_error_doesnt_show_optional_columns(
     )
 
 
+def test_check_messages_adds_sender_id_in_session_to_metadata(
+    client_request,
+    mocker,
+    mock_get_live_service,
+    mock_get_service_template,
+    mock_get_users_by_service,
+    mock_get_service_statistics,
+    mock_get_job_doesnt_exist,
+    mock_s3_set_metadata,
+    fake_uuid,
+):
+    mocker.patch('app.main.views.send.s3download', return_value=(
+        'phone number,\n07900900321'
+    ))
+    mocker.patch('app.main.views.send.get_sms_sender_from_session')
+
+    with client_request.session_transaction() as session:
+        session['file_uploads'] = {
+            fake_uuid: {'template_id': fake_uuid}
+        }
+        session['sender_id'] = 'fake-sender'
+
+    client_request.get(
+        'main.check_messages',
+        service_id=SERVICE_ONE_ID,
+        template_id=fake_uuid,
+        upload_id=fake_uuid,
+        original_file_name='example.csv',
+        _test_page_title=False,
+    )
+
+    mock_s3_set_metadata.assert_called_once_with(
+        SERVICE_ONE_ID,
+        fake_uuid,
+        notification_count=1,
+        template_id=fake_uuid,
+        sender_id='fake-sender',
+        valid=True,
+        original_file_name='example.csv',
+    )
+
+
 @pytest.mark.parametrize('extra_args', (
     {},
     {'from_test': True},