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) {
    alert("Het email adres is ongeldig")
    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("Het email adres is ongeldig")
      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("Het email adres is ongeldig")
  				 return false
        }
      }
      return true
  }
  var domainArray=domain.match(domainPat)
  if (domainArray==null) {
  	 	alert("Het email adres is ongeldig")
      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) {
     alert("Het emailadres moet eindigen op een drieletterig domein of een tweeletterige landcode.")
     return false
  }
  if (len<2) {
     var errStr="Het emailadres heeft geen domeinnaam."
     alert(errStr)
     return false
  }
  return true;
}