function emailCheck (emailStr){var emailPat=/^(.+)@(.+)$/;var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";var validChars="\[^\\s" + specialChars + "\]";var quotedUser="(\"[^\"]*\")";var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;var atom=validChars + '+';var word="(" + atom + "|" + quotedUser + ")";var userPat=new RegExp("^" + word + "(\\." + word + ")*$");var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");var matchArray=emailStr.match(emailPat);if (matchArray==null){alert("Email address seems incorrect (check @ and .'s)");return false;}var user=matchArray[1];var domain=matchArray[2];if (user.match(userPat)==null){alert("The email username doesn't seem to be valid.");return false;}var IPArray=domain.match(ipDomainPat);if (IPArray!=null){for (var i=1;i<=4;i++){if (IPArray[i]>255){alert("Email Destination IP address is invalid!");return false;}}return true;}var domainArray=domain.match(domainPat);if (domainArray==null){alert("The email domain name doesn't seem to be valid.");return false;}var atomPat=new RegExp(atom,"g");var domArr=domain.match(atomPat);var len=domArr.length;if (domArr[domArr.length-1].length<2 || domArr[domArr.length-1].length>3){alert("The email address must end in a three-letter domain, or two letter country.");return false;}if (len<2){var errStr="This email address is missing a hostname!";alert(errStr);return false;}return true;}