function isEmail (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. 
   These characters include ( ) < > @ , ; : \ " . [ ]    */
   var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"

   /* The following string represents the range of characters allowed in a 
   username or domainname.  */
   var validChars="\[^\\s" + specialChars + "\]"

   /* The following pattern applies if the "user" is a quoted string */ 
   var quotedUser="(\"[^\"]*\")"


   /* The following pattern applies for domains that are IP addresses*/
      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. */
  
   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 +")*$")


   /* checking valid email address */  
   var matchArray=emailStr.match(emailPat)
   if (matchArray==null) 
   {
     /* Too many/few @'s */
        alert("Email address seems incorrect (check @ and .'s)")
        document.bm.mail.value='';
        document.bm.mail.focus();
        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.")
     document.bm.mail.value='';
     document.bm.mail.focus();
     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!")
         document.bm.mail.value='';
         document.bm.mail.focus();
         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.")
     document.bm.mail.value='';
     document.bm.mail.focus();
      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 email must end in a two letter or three letter word.
     alert("The email must end in a three-letter domain, or two letter country.")
     document.bm.mail.value='';
     document.bm.mail.focus();
     return false
   }

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

   return true;
}
//  End -->