diff --git a/certbot-postfix/certbot_postfix/installer.py b/certbot-postfix/certbot_postfix/installer.py
index 60c8b3109..910fa67a6 100644
--- a/certbot-postfix/certbot_postfix/installer.py
+++ b/certbot-postfix/certbot_postfix/installer.py
@@ -55,6 +55,7 @@ class Installer(plugins_common.Installer):
             self._verify_executable_is_available(param)
         self._set_config_dir()
         self._check_version()
+        self.config_test()
         self._lock_config_dir()
 
     def _verify_executable_is_available(self, config_name):
diff --git a/certbot-postfix/certbot_postfix/installer_test.py b/certbot-postfix/certbot_postfix/installer_test.py
index a7a9d27fa..425f0dd54 100644
--- a/certbot-postfix/certbot_postfix/installer_test.py
+++ b/certbot-postfix/certbot_postfix/installer_test.py
@@ -61,6 +61,7 @@ class InstallerTest(certbot_test_util.ConfigTestCase):
         expected = self.config.postfix_config_dir
         self.config.postfix_config_dir = None
 
+        check_call_path = "certbot_postfix.installer.subprocess.check_call"
         check_output_path = "certbot_postfix.installer.util.check_output"
         exe_exists_path = "certbot_postfix.installer.certbot_util.exe_exists"
         with mock.patch(check_output_path) as mock_check_output:
@@ -68,7 +69,8 @@ class InstallerTest(certbot_test_util.ConfigTestCase):
                 "config_directory = " + expected, "mail_version = 3.1.4"
             ]
             with mock.patch(exe_exists_path, return_value=True):
-                installer.prepare()
+                with mock.patch(check_call_path):
+                    installer.prepare()
         self.assertEqual(installer.config_dir, expected)
 
     def test_lock_error(self):
@@ -159,12 +161,14 @@ class InstallerTest(certbot_test_util.ConfigTestCase):
         """
         installer = self._create_installer()
 
+        check_call_path = "certbot_postfix.installer.subprocess.check_call"
         check_output_path = "certbot_postfix.installer.util.check_output"
         exe_exists_path = "certbot_postfix.installer.certbot_util.exe_exists"
         with mock.patch(check_output_path) as mock_check_output:
             with mock.patch(exe_exists_path, return_value=True):
-                mock_check_output.return_value = "mail_version = 3.1.4"
-                installer.prepare()
+                with mock.patch(check_call_path):
+                    mock_check_output.return_value = "mail_version = 3.1.4"
+                    installer.prepare()
 
         return installer