function emailCheck(emailStr) {

// checks if the e-mail address is valid
var emailPat = /^(\".*\"|[A-Za-z]\w*)@(\[\d{1,3}(\.\d{1,3}){3}]|[A-Za-z]\w*(\.[A-Za-z]\w*)+)$/;
var matchArray = emailStr.match(emailPat);

if (emailStr == "") {
	return true;
}else{
	if (matchArray == null) {
	alert("There may be a typo in your email address.  Please double check it.");
	return false;
}
}
// make sure the IP address domain is valid
var IPArray = matchArray[2].match(/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/);
if (IPArray != null) {
for (var i=1;i<=4;i++) {
if (IPArray[i]>255) {
alert("Destination IP address is invalid!")
return false;
      }
   }
}
return true;
}