function emailCheck (emailStr) {

var checkTLD=1;

var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;

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];

for (i=0; i<user.length; i++) {
if (user.charCodeAt(i)>127) {
alert("Ths username contains invalid characters.");
return false;
   }
}
for (i=0; i<domain.length; i++) {
if (domain.charCodeAt(i)>127) {
alert("Ths domain name contains invalid characters.");
return false;
   }
}

// See if "user" is valid 

if (user.match(userPat)==null) {

// user is not valid

alert("The username doesn't seem to be valid.");
return false;
}

/* if the e-mail address is at an IP address (as opposed to a symbolic
host name) make sure the IP address is valid. */

var IPArray=domain.match(ipDomainPat);
if (IPArray!=null) {

// this is an IP address

for (var i=1;i<=4;i++) {
if (IPArray[i]>255) {
alert("Destination IP address is invalid!");
return false;
   }
}
return true;
}

// Domain is symbolic name.  Check if it's valid.
 
var atomPat=new RegExp("^" + atom + "$");
var domArr=domain.split(".");
var len=domArr.length;
for (i=0;i<len;i++) {
if (domArr[i].search(atomPat)==-1) {
alert("The domain name does not seem to be valid.");
return false;
   }
}

if (checkTLD && domArr[domArr.length-1].length!=2 && 
domArr[domArr.length-1].search(knownDomsPat)==-1) {
alert("The address must end in a well-known domain or two letter " + "country.");
return false;
}

// Make sure there's a host name preceding the domain.

if (len<2) {
alert("This address is missing a hostname!");
return false;
}

// If we've gotten this far, everything's valid!
return true;
}