diff --git a/app/authentication/auth.py b/app/authentication/auth.py
index b1b269b5c..8242795b2 100644
--- a/app/authentication/auth.py
+++ b/app/authentication/auth.py
@@ -47,11 +47,14 @@ def restrict_ip_sms():
     ip = ''
     if request.headers.get("X-Forwarded-For"):
         # X-Forwarded-For looks like "203.0.113.195, 70.41.3.18, 150.172.238.178"
-        ip_list = request.headers.get("X-Forwarded-For")
-        ip = ip_list.split(',')[0].strip()
-        current_app.logger.info("Inbound sms ip list {}".format(ip_list))
+        # Counting backwards and look at the IP at the 3rd last hop - hence, hop(end-3)
+        ip_route = request.headers.get("X-Forwarded-For")
+        ip_list = ip_route.split(',')
+        if len(ip_list) >= 3:
+            ip = ip_list[len(ip_list) - 3]
+        current_app.logger.info("Inbound sms ip route list {}".format(ip_route))
 
-    if ip in current_app.config.get('ALLOW_IP_INBOUND_SMS'):
+    if ip in current_app.config.get('SMS_INBOUND_WHITELIST'):
         current_app.logger.info("Inbound sms ip addresses {} passed ".format(ip))
         return
     else:
diff --git a/app/cloudfoundry_config.py b/app/cloudfoundry_config.py
index 9d918928b..1868924ab 100644
--- a/app/cloudfoundry_config.py
+++ b/app/cloudfoundry_config.py
@@ -43,6 +43,7 @@ def extract_notify_config(notify_config):
     os.environ['SECRET_KEY'] = notify_config['credentials']['secret_key']
     os.environ['DANGEROUS_SALT'] = notify_config['credentials']['dangerous_salt']
     os.environ['PERFORMANCE_PLATFORM_TOKEN'] = notify_config['credentials'].get('performance_platform_token', '')
+    os.environ['SMS_INBOUND_WHITELIST'] = notify_config['credentials']['allow_ip_inbound_sms']
 
 
 def extract_notify_aws_config(aws_config):
diff --git a/app/config.py b/app/config.py
index 03c577bfc..94950155f 100644
--- a/app/config.py
+++ b/app/config.py
@@ -262,7 +262,7 @@ class Config(object):
 
     FREE_SMS_TIER_FRAGMENT_COUNT = 250000
 
-    ALLOW_IP_INBOUND_SMS = []
+    SMS_INBOUND_WHITELIST = os.environ.get('SMS_INBOUND_WHITELIST', [])
 
 
 ######################
diff --git a/tests/app/authentication/test_authentication.py b/tests/app/authentication/test_authentication.py
index 32bb47327..e423ab9a2 100644
--- a/tests/app/authentication/test_authentication.py
+++ b/tests/app/authentication/test_authentication.py
@@ -313,8 +313,7 @@ def __create_token(service_id):
 def restrict_ip_sms_app():
     app = flask.Flask(__name__)
     app.config['TESTING'] = True
-    app.config['ALLOW_IP_INBOUND_SMS'] = ['134.213.243.188']
-
+    app.config['SMS_INBOUND_WHITELIST'] = ['111.111.111.111', '100.100.100.100']
     blueprint = flask.Blueprint('restrict_ip_sms_app', __name__)
 
     @blueprint.route('/')
@@ -332,7 +331,7 @@ def test_allow_valid_ips(restrict_ip_sms_app):
     response = restrict_ip_sms_app.get(
         path='/',
         headers=[
-            ('X-Forwarded-For', '134.213.243.188, 222.222.222.222, 127.0.0.1'),
+            ('X-Forwarded-For', '111.111.111.111, 222.222.222.222, 127.0.0.1'),
         ]
     )
 
@@ -345,7 +344,20 @@ def test_reject_invalid_ips(restrict_ip_sms_app):
         restrict_ip_sms_app.get(
             path='/',
             headers=[
-                ('X-Forwarded-For', '222.222.222.222, 111.111.111.111, 127.0.0.1')
+                ('X-Forwarded-For', '222.222.222.222, 333.333.333.333, 127.0.0.1')
+            ]
+        )
+
+    assert exc_info.value.short_message == 'Unknown source IP address from the SMS provider'
+
+
+@pytest.mark.xfail(reason='Currently not blocking invalid IPs', strict=True)
+def test_illegitimate_ips(restrict_ip_sms_app):
+    with pytest.raises(AuthError) as exc_info:
+        restrict_ip_sms_app.get(
+            path='/',
+            headers=[
+                ('X-Forwarded-For', '111.111.111.111, 999.999.999.999, 333.333.333.333, 127.0.0.1')
             ]
         )
 
diff --git a/tests/app/test_cloudfoundry_config.py b/tests/app/test_cloudfoundry_config.py
index acd57796e..1c1bf3271 100644
--- a/tests/app/test_cloudfoundry_config.py
+++ b/tests/app/test_cloudfoundry_config.py
@@ -16,7 +16,8 @@ def notify_config():
             'admin_client_secret': 'admin client secret',
             'secret_key': 'secret key',
             'dangerous_salt': 'dangerous salt',
-            'performance_platform_token': 'performance platform token'
+            'performance_platform_token': 'performance platform token',
+            'allow_ip_inbound_sms': ['111.111.111.111', '100.100.100.100']
         }
     }
 
@@ -197,3 +198,10 @@ def test_redis_config():
 
     assert os.environ['REDIS_ENABLED'] == '1'
     assert os.environ['REDIS_URL'] == 'redis url'
+
+
+@pytest.mark.usefixtures('os_environ', 'cloudfoundry_environ')
+def test_sms_inbound_config():
+    extract_cloudfoundry_config()
+
+    assert os.environ['SMS_INBOUND_WHITELIST'] == ['111.111.111.111', '100.100.100.100']