diff --git a/roles/mail_server/molecule/default/tests/test_default.py b/roles/mail_server/molecule/default/tests/test_default.py
index 51d1855fdd64283fcdbb7e2883cd8b6a4fdc83ed..df02ca9dffe1b9e34e166dabc5ec4c210f2386b5 100644
--- a/roles/mail_server/molecule/default/tests/test_default.py
+++ b/roles/mail_server/molecule/default/tests/test_default.py
@@ -229,6 +229,22 @@ 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_postfix_delivery_to_dovecot(host):
     """
     Tests if mail received by Postfix is properly delivered to Dovecot.