On the page where the iframe is inserted

 var data = {mails: 'mymail@gmail.com'}; 
 setTimeout( function(){     
 iframe.postMessage(data,'*');
 }, 3000);

PARENT

   window.addEventListener('message', function(msg) {
     jQuery("#iframe-mail_owner").val(msg.data.mails);
      console.log(msg.data.mails); 

    });

The field is filled in correctly, but after a second it becomes empty, since some other postmessage comes again with undefined And it's strange why I see recaptcha and other data in the logs, I made it clear that I output console.log(e.data.mails); not just DATA