Fixed callback not being called upon error

server.js

             params.to = recipient;
             // Send the email
             transporter.sendMail(params, (err, infos) => {
+                sent();
                 if(err) {
                     return update(err, recipient);
                 }
                 update(null, infos);
                 // Promise callback
-                sent();
             });
         });
     });