diff --git a/mail/templates/pixelegg/app.css b/mail/templates/pixelegg/app.css
index 3c2031f33b..504d3db8f5 100755
--- a/mail/templates/pixelegg/app.css
+++ b/mail/templates/pixelegg/app.css
@@ -565,6 +565,24 @@ div.mailPreviewHeaders #mail-index_previewAttachmentArea.visible {
 .mail_extraEmails.visible > a {
   display: list-item;
 }
+/**
+ * Lock div for tree to prevent further clicks
+ */
+#mail-index_nm\[foldertree\] {
+  position: relative;
+}
+#mail_folder_lock_div {
+  position: absolute;
+  left: 0;
+  top: 0;
+  width: 100%;
+  height: 100%;
+  z-index: 10000;
+  background-image: url(../../../phpgwapi/templates/default/images/ajax-loader.gif);
+  background-position: left top;
+  background-repeat: no-repeat;
+  background-color: rgba(255, 255, 255, 0.5);
+}
 #popupMainDiv {
   padding: 5px;
 }