当Ajax表单再次提交php中的现有记录时，如何防止

I am having a PHP website, here 2 radio button is available. When first check box contains remarks text box with submit button available. Second check box contains the email text box with submit button available. here when I click this email button, it will send mail correctly at first time. After that I have to change the second email in text box and click submit button, now it will send existing email id first time and send new email next time. How can I restrict here in jquery?

function callfunction(ivalue) {
  var sendurl = 'ajaxpage.php?msg='+msg;
  $("#frm_sms_email_"+ivalue).on('submit', function(e) {
     e.preventDefault();
     $.ajax({
        type: "POST",
        data:  new FormData(this),
        contentType: false,
        cache: false,
        processData:false,
        url: sendurl,
        success: function(data){
        },
        error: function(){}
        });
     });
  }
}