function emailCheck (emailStr) {
	emailStr = emailStr.toLowerCase();
	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];

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

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

	/* 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) {
	    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;
	}

}