need a confirmation text to appear on email submission

Simply add a Success callback to your Ajax function:

     $('#sendEmail').click(function(){
             $.ajax({
                 type: 'POST',
                 url: 'www.example.com/email.php',
                 data: { content: $('#email-data').html()},
                 success:  function(data) {
                 //data variable can be used if your ajax call returns something
                     do_stuff_here();
                 }
             });
          });

In your case, you could do something like

success:  function() {
    $('body').append('<div class="success">Success!</div>');
}

However, is there a reason you don’t want to use a and the .submit() method?
(http://api.jquery.com/submit/)

Also, don’t forget to validate 🙂