Edit in JSFiddle

Result
JavaScript
CSS
HTML

$('.email').each(function(i) {
    var mail = $(this).html();
    mail = mail.replace(" [at] ", "@");
    mail = mail.replace(" [dot] ", ".");
    $(this).html(mail).replaceWith("<a href=\"mailto:" + $(this).text() + "\">" + $(this).text() + "</a>");
});

p{margin: 25px ;}

<p> Email : <em class="email">foo [at] example [dot] com</em></p>