diff --git a/doc/installation/deployment.md b/doc/installation/deployment.md
index 46bb5b26c4c7c807a8794cf6d5a1acaea99ec010..d6116c5bfc3b216927fe8e2c18c7ed2683d645fb 100644
--- a/doc/installation/deployment.md
+++ b/doc/installation/deployment.md
@@ -67,7 +67,7 @@ If you have your own wildcard certificate, you already have cert-manager install
 have some other way of obtaining TLS certificates, [read about more TLS options here](./tls.md).
 
 For the default configuration, you must specify an email address to register your TLS
-certificates.
+certificates. Please note that the mail domain must be the same as the value specified in `global.hosts.domain`.
 *Include these options in your Helm install command:*
 
 ```