--- /home/dm_50/sites/all/modules/email/email.module    2008-04-15 07:56:09.000000000 -0400
+++ ./email.module      2008-11-05 13:26:34.000000000 -0500
@@ -113,6 +113,13 @@
         '#required' => FALSE,
         '#description' => t('Size of textfield'),
       );
+      $form['extra_validation'] = array(
+        '#type' => 'checkbox',
+        '#title' => t('Extended validation?'),
+        '#default_value' => isset($widget['extra_validation']) ? $widget['extra_validation'] : 0,
+        '#required' => FALSE,
+        '#description' => t('Apply more stringent tests to the email address (requires a FQDN that actually exists).'),
+      );

       return $form;

@@ -123,7 +130,7 @@
       break;

     case 'save':
-      return array('size');
+      return array('size','extra_validation');
   }
 }

@@ -182,6 +189,15 @@
         foreach ($node_field as $delta => $item) {
           if ($item['email'] != '' && !valid_email_address(trim($item['email']))) {
             form_set_error($field['field_name'],t('"%mail" is not a valid email address',array('%mail' => $item['email'])));
+            $item['email'] = '';
+          }
+
+          if ($field['widget']['extra_validation'] && $item['email'] != '') {
+            $FQDN = '/^(?:[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])+(?:\.(?:[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])+)*(?:\.[a-zA-Z]{2,})$/';
+            list($mailbox,$domain) = split('@', trim($item['email']));
+            if(!preg_match($FQDN, $domain) || !checkdnsrr($domain .'.', 'MX')) {
+              form_set_error($field['field_name'],t('"%mail"  does not contain a valid domain',array('%mail' => $item['email'])));
+            }
           }
         }
       }