diff --git a/lib/AutodiscoverJson.php b/lib/AutodiscoverJson.php
--- a/lib/AutodiscoverJson.php
+++ b/lib/AutodiscoverJson.php
@@ -29,40 +29,49 @@
 class AutodiscoverJson extends Autodiscover
 {
 
+    /**
+     * process incoming request
+     */
     public function handle_request()
     {
         Log::debug('Request [json]: ' . $_SERVER['REQUEST_URI']);
 
-        $supportedProtocols = array('autodiscoverv1' => 'AutodiscoverV1');
-        if ($this->conf->get('autodiscover', 'activesync')) {
-            $supportedProtocols['activesync'] = 'ActiveSync';
+        // check protocol (at this state we don't know if autodiscover is configured)
+        $allowedProtocols = ['activesync', 'autodiscoverv1'];
+        if (empty($_GET['Protocol'])) {
+            $this->error(
+                "A valid value must be provided for the query parameter 'Protocol'",
+                'MandatoryParameterMissing'
+            );
         }
-
-        $protocol = isset($_GET['Protocol']) ? $_GET['Protocol'] : '';
-
-        // Exit early on unsupported protocol
-        if (empty($protocol) || !isset($supportedProtocols[strtolower($protocol)])) {
-            $json = array(
-                'ErrorCode' => 'ProtocolNotSupported',
-                'ErrorMessage' => 'The given protocol value \u0027' . $protocol . '\u0027 is invalid.'
-                    . ' Supported values are \u0027' . implode(',', $supportedProtocols) . '\u0027'
+        elseif (!in_array(strtolower($_GET['Protocol']), $allowedProtocols)) {
+            $this->error(
+                sprintf(
+                    "The given protocol value '%s' is invalid. Supported values are '%s'",
+                    $_GET['Protocol'],
+                    implode(",", $allowedProtocols)
+                ),
+                'InvalidProtocol'
             );
-
-            $response = json_encode($json, JSON_PRETTY_PRINT);
-            Log::debug('Response [json]: ' . $response);
-
-            http_response_code(400);
-            header('Content-Type: application/json; charset=' . Autodiscover::CHARSET);
-            echo $response;
-            exit;
         }
 
+        // check email
         if (preg_match('|autodiscover.json/v1.0/([^\?]+)|', $_SERVER['REQUEST_URI'], $regs)) {
             $this->email = $regs[1];
         }
-        else if (!empty($_GET['Email'])) {
+        elseif (!empty($_GET['Email'])) {
             $this->email = $_GET['Email'];
         }
+        elseif (!empty($_GET['email'])) {
+            $this->email = $_GET['email'];
+        }
+
+        if (empty($this->email) || !strpos($this->email, '@')) {
+            $this->error(
+                'A valid smtp address must be provided',
+                'MandatoryParameterMissing'
+            );
+        }
     }
 
     /**
@@ -70,9 +79,18 @@
      */
     protected function handle_response()
     {
-        if (strtolower($_GET['Protocol']) == 'activesync'
-            && !empty($this->config['activesync'])
-        ) {
+        if (strtolower($_GET['Protocol']) == 'activesync') {
+            // throw error if activesync is disabled
+            if (empty($this->config['activesync'])) {
+                $this->error(
+                    sprintf(
+                        "The given protocol value '%s' is invalid. Supported values are '%s'",
+                        $_GET['Protocol'], 'autodiscoverv1'
+                    ),
+                    'InvalidProtocol'
+                );
+            }
+
             if (!preg_match('/^https?:/i', $this->config['activesync'])) {
                 $this->config['activesync'] = 'https://' . $this->config['activesync'] . '/Microsoft-Server-ActiveSync';
             }
@@ -88,11 +106,29 @@
             );
         }
 
-        $response = json_encode($json, JSON_PRETTY_PRINT);
+        $response = json_encode($json, JSON_PRETTY_PRINT | JSON_HEX_APOS | JSON_HEX_QUOT);
         Log::debug('Response [json]: ' . $response);
 
         header('Content-Type: application/json; charset=' . Autodiscover::CHARSET);
         echo $response;
         exit;
     }
+
+    /**
+     * Send error to the client and exit
+     */
+    protected function error($msg, $code="InternalServerError")
+    {
+        http_response_code(400);
+        $json = array(
+            'ErrorCode' => $code,
+            'ErrorMessage' => $msg
+        );
+        $response = json_encode($json, JSON_PRETTY_PRINT | JSON_HEX_APOS | JSON_HEX_QUOT);
+        Log::debug('Error [json]: ' . $response);
+        header('Content-Type: application/json; charset=' . Autodiscover::CHARSET);
+        echo $response;
+        exit;
+    }
+
 }
diff --git a/lib/AutodiscoverMicrosoft.php b/lib/AutodiscoverMicrosoft.php
--- a/lib/AutodiscoverMicrosoft.php
+++ b/lib/AutodiscoverMicrosoft.php
@@ -121,6 +121,42 @@
         exit;
     }
 
+    /**
+     * Send error to the client and exit
+     */
+    protected function error($msg)
+    {
+        $xml = new DOMDocument('1.0', Autodiscover::CHARSET);
+        $doc = $xml->createElementNS(self::NS, 'Autodiscover');
+        $doc = $xml->appendChild($doc);
+
+        $response = $xml->createElement('Response');
+        $response = $doc->appendChild($response);
+
+        $error = $xml->createElement('Error');
+        list($usec, $sec) = explode(' ', microtime());
+        $error->setAttribute('Time',date('H:i:s',$sec).".".substr($usec, 2, 6));
+        $error->setAttribute('Id',sprintf("%u",crc32($_SERVER['HTTP_HOST'])));
+        $response->appendChild($error);
+
+        $code = $xml->createElement('ErrorCode');
+        $code->appendChild($xml->createTextNode(600));
+        $error->appendChild($code);
+
+        $message = $xml->createElement('Message');
+        $message->appendChild($xml->createTextNode($msg));
+        $error->appendChild($message);
+
+        $response->appendChild($xml->createElement('DebugData'));
+
+        $xml->formatOutput = true;
+        Log::debug('Error [microsoft]: ' . $msg);
+
+        header('Content-type: text/xml; charset=' . Autodiscover::CHARSET);
+        echo $xml->saveXML();
+        exit;
+    }
+
     /**
      * Generates XML response for Activesync
      */