JSFiddle - React, Tailwind, and code Playground

JavaScript

function validateEmail(email) {
    var re = /^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i;
    return re.test(email);
}


var string = "abc@abc.com;abc@abc.com; abc@a@bc.com ; abc@abc.com ;abc@abc.com;"

var emails = string.split(';');

var invalidEmails = [];

for (i = 0; i < emails.length; i++) { 
    if(!validateEmail(emails[i].trim())) {
      invalidEmails.push(emails[i].trim())
    }
}

alert(invalidEmails);