Update runtime files
diff --git a/runtime/indent/mail.vim b/runtime/indent/mail.vim
index 6246b40..22bb0f7 100644
--- a/runtime/indent/mail.vim
+++ b/runtime/indent/mail.vim
@@ -1,7 +1,7 @@
" Vim indent file
" Language: Mail
" Maintainer: Bram Moolenaar
-" Last Change: 2009 Jun 03
+" Last Change: 2021 Sep 26
if exists("b:did_indent")
finish
@@ -11,3 +11,5 @@
" What works best is auto-indenting, disable other indenting.
" For formatting see the ftplugin.
setlocal autoindent nosmartindent nocindent indentexpr=
+
+let b:undo_indent = "setl ai< cin< inde< si<"