(function(exports) {

  if (location != 'chrome://messenger/content/messenger.xhtml') return;

  window.addEventListener("MsgLoaded", ()=>{
console.log('event: MsgLoaded');
    const ramv=gTabmail.currentAboutMessage.document.getElementById('hdrReplyAllButton');
    const h=ramv.getAttribute('hidden');
console.log('replyAll: '+ramv+' hidden='+h);

    const raut=document.querySelector('li[item-id="reply-all"]');
    if (h) {  //replyAll is hidden
      raut.setAttribute('disabled', 'true');
    } else {
      raut.removeAttribute('disabled');
    }
  });

})(this);