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<!-- Changes:  Sandeep V. Tamhankar (stamhankar@hotmail.com) -->

/*
   1.1.2: Fixed a bug where trailing . in e-mail address was passing
            (the bug is actually in the weak regexp engine of the browser; I
            simplified the regexps to make it work).
   1.1.1: Removed restriction that countries must be preceded by a domain,
          so abc@host.uk is now legal.  However, there's still the 
          restriction that an address must end in a two or three letter
          word.
     1.1: Rewrote most of the function to conform more closely to RFC 822.
     1.0: Original
*/

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<!-- The JavaScript Source!! http://javascript.internet.com -->

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
		return("* Email address seems incorrect (check @ and .'s)")
	}
	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
		return("* The username doesn't seem to be valid.")			
	}

	/* 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("* Destination IP address is invalid!")
		    }
	    }
	    return('');
	}
	
	// Domain is symbolic name
	var domainArray=domain.match(domainPat)
	if (domainArray==null) {
		//alert("The domain name doesn't seem to be valid.")
	    //return false
		return("* The domain name on your email address doesn't seem to be valid.")
	}
	
	/* 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>4) {
	   // the address must end in a two letter or three letter word.
	   //alert("The address must end in a three or four letter domain, or two letter country.")
	   //return false
	   return("* Email address must end in a three-letter or four-letter domain, or two letter country.")
	}
	
	// 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
	   return("* Email address is missing a hostname!")
	}
	
	// If we've gotten this far, everything's valid!
	//return true;
	return('');
}

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