diff --git a/POSTINSTALL.md b/POSTINSTALL.md
index 5b0cf6b..f65f58b 100644
--- a/POSTINSTALL.md
+++ b/POSTINSTALL.md
@@ -1,5 +1,6 @@
 This application integrates with Cloudron authentication.
 However, all Cloudron users share the same Syncthing session.
+Please note that only the username is accepted as login and not the email address.
 
 Syncthing contains an internal user `admin` that is needed by Cloudron but not exposed. 
 Please do not change the password of that account.