// JavaScript Documentfunction emailCheck (emailStr) {
<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->

<!-- V1.1.3: Sandeep V. Tamhankar (stamhankar@hotmail.com) -->
<!-- Original:  Sandeep V. Tamhankar (stamhankar@hotmail.com) -->
<!-- modified: www.sixspots.net -->

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);
var message 
if (matchArray==null) {

message = "Email address seems incorrect (check @ and .'s)";
return message;
}
var user=matchArray[1];
var domain=matchArray[2];

// Start by checking that only basic ASCII characters are in the strings (0-127).

for (i=0; i<user.length; i++) {
if (user.charCodeAt(i)>127) {
message = "Ths email address contains invalid characters.";
return message;
   }
}
for (i=0; i<domain.length; i++) {
if (domain.charCodeAt(i)>127) {
message = "The email address domain name contains invalid characters.";
return message;
   }
}

// See if "user" is valid 

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

// user is not valid

message = "The email address doesn't seem to be valid.";
return message;
}

/* 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) {
message = "Destination IP address is invalid!";
return message;
   }
}
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) {
message = "The email address domain name does not seem to be valid.";
return message;
   }
}

/* domain name seems valid, but now make sure that it ends in a
known top-level domain (like com, edu, gov) or a two-letter word,
representing country (uk, nl), and that there's a hostname preceding 
the domain or country. */

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

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

if (len<2) {
message = "The email address is missing a hostname!";
return message;
}

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