diff --git a/Classes/Controller/SsoController.php b/Classes/Controller/SsoController.php
index 6cb1d42..0fc607c 100644
--- a/Classes/Controller/SsoController.php
+++ b/Classes/Controller/SsoController.php
@@ -133,6 +133,13 @@ class SsoController extends ActionController
             }
 
             if (is_array($user) === true) {
+                if (is_null($user['email']) || strlen($user['email']) < 4) {
+                    $errorText = '<div><b>ERROR!</b><br>' .
+                                 'You did not enter your email address to your personal properties.<br>' .
+                                 'The forum cannot be used without a valid email address.<br>';
+                    GeneralUtility::devLog('authenticateAction: email address not available', $extKey, 2, array('error' => $errorText));
+                    return $errorText;
+                }
                 $userId      = $user['uid'];
                 $userEmail   = $user['email'];
                 $userName    = $user['username'];
@@ -159,12 +166,10 @@ class SsoController extends ActionController
                     .'You should not see this message!<br />'
                     .'This plugin should be made available only, if a Frontend User is logged in.<br />'
                     .'Please change this in the setup of this content element.';
-                GeneralUtility::devLog('authenticateAction bad configuration', $extKey, 2, array('error' => $errorText));
+                GeneralUtility::devLog('authenticateAction: bad configuration', $extKey, 2, array('error' => $errorText));
                 return $errorText;
             }//end if
         }//end if
-
+        return '<div><b>Internal Error!</b><br>Unreachable code.</div>';
     }//end authenticateAction()
-
-
 }