gentoo-overlay/mail-mta/exim/files/exim-4.94-maildir.patch

--- a/src/configure.default
+++ b/src/configure.default
@@ -873,7 +873,9 @@
 
 local_delivery:
   driver = appendfile
-  file = /var/mail/$local_part_data
+# file = /var/mail/$local_part_data
+  directory = /home/$local_part_data/.maildir
+  maildir_format
   delivery_date_add
   envelope_to_add
   return_path_add