<!-- 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  */

<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->

<!-- Begin
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("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's valid!
  return true;
}
//  End -->

function emailCheckAllowEmpty (emailStr) {
  if (emailStr=="") {
     return true;
  }
  return emailCheck (emailStr);
}