diff --git a/POSTINSTALL.md b/POSTINSTALL.md
index 3a42f0d..e14c10c 100644
--- a/POSTINSTALL.md
+++ b/POSTINSTALL.md
@@ -1,4 +1,6 @@
-Accounts are created with the username and the full domain (including subdomain)
-under which this app is installed. e.g. `@username@mastodon.domain.com`. This subdomain
-cannot be changed later as it breaks federation.
+Accounts are created with the username and the subdomain under which this app is installed
+ e.g. `@$CLOUDRON-USERNAME@$CLOUDRON-APP-DOMAIN`. Note that Mastodon does allow this subdomain
+to be changed later as it breaks federation. So, you have to install Mastodon in the correct
+subdomain from the get-go.
+