function mailsome1(){
  who=prompt("Enter your friends email address: \n(NASA does not collect either you or \nyour friends e-mail address)","yourfriend@their.email.address");
  validaddress = emailCheck(who);
  what="Cool NASA Satellite Imagery";
  bodytext="Check%20out%20this%20NASA%20weather%20satellite%20site%20"+window.location.href;
  parent.location.href='mailto:'+who+'?subject='+what+'&body='+bodytext+'';
}

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("Email address seems incorrect (check @ and .'s)")
  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.")
  return false
}

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!")
      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.")
  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("The address must end in a three-letter domain, or two letter country.")
   return false
}

if (len<2) {
   var errStr="This address is missing a hostname!"
   alert(errStr)
   return false
}

return true;
}