diff -r 2ee3ea69e8f1 -r 2167b9e3157a src/Pure/General/mailman.scala
--- a/src/Pure/General/mailman.scala	Fri Aug 19 16:19:59 2022 +0200
+++ b/src/Pure/General/mailman.scala	Fri Aug 19 16:46:00 2022 +0200
@@ -420,7 +420,7 @@
 
     def find_messages(dir: Path): List[Message] = {
       for {
-        file <- File.find_files(dir.file, file => file.getName.endsWith(".html"))
+        file <- File.find_files(dir.file, file => File.is_html(file.getName))
         rel_path <- File.relative_path(dir, File.path(file))
       }
       yield {