вот, то что надо:

Код:
String.prototype.isEmail = function(){
//email address has to have at least 5 chars
if (this.length < 5){return false;}
var iChars = "*|,\":<>[]{}`';()&$#%";
var eLength = this.length;
for (var i=0; i < eLength; i++) {
if (iChars.indexOf(this.charAt(i)) != -1){
trace("Invalid Email Address : Illegal Character in Email Address : -->" + this.charAt(i) + "<--.");
return false;
}
}
var atIndex = this.lastIndexOf("@");
if(atIndex < 1 || (atIndex == eLength - 1)){
trace("Invalid Email Address : Email Address must contain @ as at least the second chararcter.");
return false;
}
var pIndex = this.lastIndexOf(".");
if(pIndex < 4 || (pIndex == eLength - 1)){
trace("Invalid Email Address : Email Address must contain at least one . (period) in a valid position");
return false;
}
if(atIndex > pIndex){
this.__error = "Invalid Email Address : Email Address must be in the form of name@domain.domaintype";
return false;
}
return true;
}