diff --git a/target/dovecot/dovecot-oauth2.conf.ext b/target/dovecot/dovecot-oauth2.conf.ext
index c3128900..6998ed08 100644
--- a/target/dovecot/dovecot-oauth2.conf.ext
+++ b/target/dovecot/dovecot-oauth2.conf.ext
@@ -1,2 +1,4 @@
 introspection_url =
+# Dovecot defaults:
 introspection_mode = auth
+username_attribute = email