function checkEmail(emailStr) {
               if (emailStr.length == 0)
                  return true;
               var emailPat=/^(.+)@(.+)$/;
               var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
               var validChars="\[^\\s" + specialChars + "\]";
               var quotedUser="(\"[^\"]*\")";
               var ipDomainPat=/^(\d{1,3})[.](\d{1,3})[.](\d{1,3})[.](\d{1,3})$/;
               var atom=validChars + '+';
               var word="(" + atom + "|" + quotedUser + ")";
               var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
               var domainPat=new RegExp("^" + atom + "(\\." + atom + ")*$");
               var matchArray=emailStr.match(emailPat);

               if (matchArray == null)
                  return false;

               var user=matchArray[1];
               var domain=matchArray[2];

               if (user.match(userPat) == null)
                   return false;

               var IPArray = domain.match(ipDomainPat);
               if (IPArray != null) {
                   for (var i = 1; i <= 4; i++) {
                      if (IPArray[i] > 255)
                         return false;
                   }

                   return true;
               }

               var domainArray=domain.match(domainPat);
               if (domainArray == null)
                   return false;

               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)
                  return false;

               if (len < 2)
                  return false;

               return true;
            }