diff --git a/roles/mail_forwarder/molecule/default/tests/test_default.py b/roles/mail_forwarder/molecule/default/tests/test_default.py
index 0a33b106ca3b33d7ab85d7576cab5a9b38bcfb39..397fd500065cc4dcad49846b79c2c249fb7a9e18 100644
--- a/roles/mail_forwarder/molecule/default/tests/test_default.py
+++ b/roles/mail_forwarder/molecule/default/tests/test_default.py
@@ -1,4 +1,5 @@
 import os
+import re
 
 import testinfra.utils.ansible_runner
 
@@ -64,6 +65,22 @@ def test_postfix_main_cf_file(host):
     assert config.mode == 0o644
 
 
+def test_postfix_main_configuration_is_valid(host):
+    """
+    Tests if Postfix main configuration is valid and not producing any
+    warnings.
+    """
+
+    postconf = host.run('/usr/sbin/postconf')
+
+    # Clean-up the SSH warning from the beginning of stderr if
+    # present.
+    stderr = re.sub("^Warning: Permanently added.*?\r\n", "", postconf.stderr)
+
+    assert postconf.rc == 0
+    assert stderr == ""
+
+
 def test_services(host):
     """
     Tests if all the necessary services are enabled and running.