String.prototype.isMailAddr = function checkMailAddr() {
	var addr = this.split("@");
	if(addr.length==1 || addr.length>2) return false;
	var dom = addr[1].split(".");
	if(dom.length == 1) return false;
	var domLen = dom.length
	if(domLen>2 && (dom[domLen-1]).length==0) domLen--;
	if(dom[domLen-1].length<2 || dom[domLen-1].length>3) return false;
	for(var i=0;i<domLen;i++) { if(dom[i].length==0) return false; }

	var acc = addr[0].split(".");
	for(i=0;i<acc.length;i++) { if(acc[i].length==0) return false; }
	var okChars = "abcdefghijklmnopqrstuvwxyz";
	okChars += okChars.toUpperCase()+"0123456789-_";
	var testString = acc.join("")+"."+dom.join("");
	if("."==testString) return false;
	i=0;
	while( i<testString.length ) { 
		if('.'==testString.substr(i,1)) {
			okChars = okChars.substr(0,okChars.length-1);
		} else {
			if(okChars.indexOf(testString.substr(i,1))==-1 ) return false;
		}
		i++;
	}
	return true;
}