function chk(emailStr) {
  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>5) {
    return false
  }
  
  if (len<2)
    return false
  
  return true;
}