diff --git a/roles/mail_forwarder/playbook.yml b/roles/mail_forwarder/playbook.yml
index 3d0a337a35a9dcd0998d7aa48cc6eeede28170e5..2fc2b90126a3d8f4c6577b754c8667258ae2fd54 100644
--- a/roles/mail_forwarder/playbook.yml
+++ b/roles/mail_forwarder/playbook.yml
@@ -99,6 +99,10 @@
         name: swaks
         state: installed
 
+    - name: Set-up port forwarding
+      command: "iptables -t nat -A PREROUTING -p tcp -m tcp --dport 27 -j REDIRECT --to-ports 25"
+      changed_when: False
+
   handlers:
 
     - name: Update CA certificate cache
@@ -123,6 +127,7 @@
         root: "root testuser"
       smtp_from_relay_allowed: True
       smtp_relay_host: mail-server
+      smtp_relay_host_port: 27
       smtp_relay_truststore: "{{ lookup('file', 'tests/data/x509/ca.cert.pem') }}"
 
       # common