do not use .finally() because of Node v8

lib/message-handler.js

@@ -493,15 +493,20 @@ class MessageHandler {
                                                         }
                                                     };
 
-                                                    return processAudits().finally(() => {
+                                                    let next = () => {
-                                                        return cleanup(null, true, {
+                                                        cleanup(null, true, {
                                                             uidValidity,
                                                             uid,
                                                             id: messageData._id,
                                                             mailbox: mailboxData._id,
                                                             status: 'new'
                                                         });
-                                                    });
+                                                    };
+
+                                                    // do not use more suitable .finally() as it is not supported in Node v8
+                                                    return processAudits()
+                                                        .then(next)
+                                                        .catch(next);
                                                 }
                                             );
                                         });