diff --git a/mail/templates/default/app.css b/mail/templates/default/app.css
index 6fd803b373..f1a44cfe86 100644
--- a/mail/templates/default/app.css
+++ b/mail/templates/default/app.css
@@ -1072,7 +1072,10 @@ div#mail-index_nm.splitter-pane {min-height: 100px;}
 	border: none;
 }
 #popupMainDiv {height: 100%}
-.treeContainer {height: calc(100% - 100px)}
+.treeContainer {
+	height: calc(100% - 10px);
+	overflow-y: auto;
+}
 #mail-index_mail-index-header_right {gap: 1ex;}
 #mail-index_mail-index-header_right et2-details.vacationnotice {
 	min-width: 8em;