function emailCheck (emailStr) {
var emailPat = /^(.+)@(.+)$/;
/* The following string represents the pattern for matching all special
   characters.  We don't want to allow special characters in the address.
   These characters include ( ) < > @ , ; : \ " . [ ]    */
var specialChars = "\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
/* The following string represents the range of characters allowed in a
   username or domain name.  It really states which chars aren't allowed. */
var validChars="\[^\\s" + specialChars + "\]";
/* The following pattern applies if the "user" is a quoted string (in
   which case, there are no rules about which characters are allowed
   and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
   is a legal e-mail address. */
var quotedUser="(\"[^\"]*\")";
/* The following pattern applies for domains that are IP addresses,
   rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
   e-mail address. NOTE: The square brackets are required. */
var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
/* The following string represents an atom (basically a series of
   non-special characters.) */
var atom=validChars + '+';
/* The following string represents one word in the typical username.
   For example, in john.doe@somewhere.com, john and doe are words.
   Basically, a word is either an atom or quoted string. */
var word="(" + atom + "|" + quotedUser + ")";
// The following pattern describes the structure of the user
var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
/* The following pattern describes the structure of a normal symbolic
   domain, as opposed to ipDomainPat, shown above. */
var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");

/* Begin with the coarse pattern to simply break up user@domain into
   different pieces that are easy to analyze. */
var matchArray=emailStr.match(emailPat);
if (matchArray==null) {
  /* Too many/few @'s or something; basically, this address doesn't
     even fit the general mould of a valid e-mail address. */
	alert("Email address seems incorrect (check @ and .'s)");
	return false;
}
var user=matchArray[1];
var domain=matchArray[2];

// 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
var domainArray=domain.match(domainPat);
if (domainArray==null) {
	//alert("The domain name doesn't seem to be valid.")
    return false;
}

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

/* Now we need to break up the domain to get a count of how many atoms
   it consists of. */
var atomPat=new RegExp(atom,"g");
var domArr=domain.match(atomPat);
var len=domArr.length;
if (domArr[domArr.length-1].length<2 ||
    domArr[domArr.length-1].length>3) {
   // the address must end in a two letter or three letter word.
   //alert("The address must end in a three-letter domain, or two letter country.")
   return false;
}

// Make sure there's a host name preceding the domain.
if (len<2) {
   //var errStr="This address is missing a hostname!"
   //alert(errStr)
   return false;
}

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