diff --git a/README.md b/README.md
index 9fa9f8e..ab77e83 100644
--- a/README.md
+++ b/README.md
@@ -37,3 +37,9 @@ oauth2_refresh_token = <the contents of the refresh_token file from step 2>
 ```
 
 Note: in practice you should store your token in some type of secure key store.
+
+Optionally you may want to include
+```ini
+folderfilter = lambda folder: not folder.startswith('Calendar') and not folder.startswith('Contacts')
+```
+to filter out folders containing non-mail items.