function replaceMailtos () {
  elems = document.getElementsByTagName("*");

  for (var i = 0; i < elems.length; i++) {
    if ("mailtolink".match(elems.item(i).getAttribute("mytag"))) {
      var user = elems.item(i).getAttribute("user");

      var domain = elems.item(i).getAttribute("domain");
      if (domain == null) {
        domain = "columbia.edu"
      }

      var address = user + "@" + domain;

      var linktext = elems.item(i).getAttribute("linktext");
      if (linktext == null) {
        linktext = address;
      }

      var hyperlink = document.createElement("a");
      hyperlink.setAttribute("href","mailto:" + address);
      hyperlink.appendChild(document.createTextNode(linktext));

      elems.item(i).appendChild(hyperlink);
    }
  }
}

addBodyOnload(replaceMailtos);