function emailCheck (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;
 }