function emailCheck (emailStr) {
		/* 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)
		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("Email username address 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("Email destination IP address is invalid!")
				return false
				}
			}
			return true
		}
		
		// Domain is symbolic name
		var domainArray=domain.match(domainPat)
		if (domainArray==null) {
			alert("Email address 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("Email 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="Email address is missing a hostname!"
			 alert(errStr)
			 return false
	
		}
		
		// If we've gotten this far, everything's valid!
		return true;
	}