diff --git reroute_email.module reroute_email.module
index d4510fc..2b0eaf7 100644
--- reroute_email.module
+++ reroute_email.module
@@ -61,6 +61,20 @@ function reroute_email_settings() {
 }
 
 /**
+ * Implementation of hook_validate().
+ */
+function reroute_email_settings_validate($form, $form_state) {
+  if ($form_state['values']['reroute_email_enable'] == 1) {
+    $addresslist = preg_split('/\s/', $form_state['values']['reroute_email_address'], -1, PREG_SPLIT_NO_EMPTY);
+    foreach ($addresslist as $address) {
+      if(!valid_email_address($address)) {
+        form_set_error('reroute_email_address', t('@address is not a valid email address', array('@address' => $address)));
+      }
+    }
+  }
+}
+
+/**
  * Implements hook_mail_alter() to change the destination of outgoing emails.
  * @param array $message
  *   An array containing message with keys like 'to', 'from', 'body'.