Index: vendor/autoload.php
--- vendor/autoload.php.orig
+++ vendor/autoload.php
@@ -20,6 +20,9 @@ if (PHP_VERSION_ID < 50600) {
     );
 }
 
+define('GTOPDIR', realpath(implode(DIRECTORY_SEPARATOR, [__DIR__, '..', '..'])));
+define('UMAPI_PATH', GTOPDIR . DIRECTORY_SEPARATOR . 'grommunio-mapi-header-php');
+
 require_once __DIR__ . '/composer/autoload_real.php';
 
 return ComposerAutoloaderInit2702ec2a5742b1162f093c8e12b5dc60::getLoader();