$( "#addMemberEmail" ).click(function() {
    if(jQuery.trim($('#mListMemberEmail').val()).length > 0) {
        var checkboxId = "checkbox_" + $('#mListMemberEmail').val();
        var checkbox = '<tr><td><input type="checkbox" id="' +
                         checkboxId + '" value="' + $('#mListMemberEmail').val() +
                         '" checked/></td><td>' + $('#mListMemberEmail').val() +
                         '</td><td><div class="btndel" id="abc">delete</div></td></tr>';
        $('#group').append(checkbox);

        //reset textbox
        $('#mListMemberEmail').val('');
    } else {
        alert("Please enter an email address");
    }
});

//why this is does not work?
$( ".btndel" ).click(function() {
    alert("Aaa");
});

$(document).on("click",".btndel", function() {
    alert("Aaa");
});