// ==UserScript==
// @name           Select All
// @namespace      Outlook Web Access
// @description    Select All and delete
// @include        *?Cmd=contents*
// ==/UserScript==

// Add jQuery
var GM_JQ = document.createElement('script');
GM_JQ.src = 'http://jquery.com/src/jquery-latest.js';
GM_JQ.type = 'text/javascript';
document.getElementsByTagName('head')[0].appendChild(GM_JQ);

// Check if jQuery's loaded
function GM_wait() {
    if(typeof unsafeWindow.jQuery == 'undefined') { window.setTimeout(GM_wait,100); }
else { $ = unsafeWindow.jQuery; letsJQuery(); }
}
GM_wait();

function buildSelectAll() {

         $(".List input[type='checkbox']").each(function() {
            this.checked = true;
         });

         unsafeWindow.SetCmd (unsafeWindow.msgViewer.CmdDelete.value);

}

// All your GM code must be inside this function
function letsJQuery() {
    buildSelectAll();
}