function emailCheck(emailStr)
{
	/***********************************************************************
	The following variable tells the rest of the function whether or not
	to verify that the address ends in a two-letter country or well-known
	TLD.
	1 means check it, 0 means don't.
	************************************************************************/
	var checkTLD = 1;

	// The following is the list of known TLDs that an e-mail address must end with.
	var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;

	/***********************************************************************
	The following pattern is used to check if the entered e-mail address
	fits the user@domain format.  It also is used to separate the username
	from the domain.
	************************************************************************/
	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 domainname.  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 +")*$");

	// Finally, let's start trying to figure out if the supplied address is valid.

	/***********************************************************************
	Begin with the coarse pattern to simply break up user@domain into
	different pieces that are easy to analyze.
	***********************************************************************/
	var matchArray = emailStr.match(emailPat);

	/***********************************************************************
	Too many/few @'s or something; basically, this address doesn't
	even fit the general mould of a valid e-mail address.
	***********************************************************************/
	if(matchArray==null) {
		alert("無效な電子メールアドレスです. (e.g. 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("メールアドレス中ユーザーネームに相応しくない文字があります.");
			return false;
	   }
	}

	for(i=0; i<domain.length; i++) {
		if(domain.charCodeAt(i)>127) {
			alert("メールアドレス中ドメインに相応しくない文字があります.");
			return false;
		}
	}

	//if(user.match(userPat)==null) {
	//	alert("メールアドレス中ユーザーネームが間違いました.");
	//	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("無效なIPアドレスです.");
				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("無效なドメイン名です.");
			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("無效なドメイン名です.");
		return false;
	}

	// Make sure there's a host name preceding the domain.
	if(len<2) {
		alert("無效なドメイン名です.");
		return false;
	}

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