diff --git a/changelog.d/6423.misc b/changelog.d/6423.misc
new file mode 100644
index 0000000000000000000000000000000000000000..9bcd5d36c1326bbbb605e7abcfd100eb389a0f13
--- /dev/null
+++ b/changelog.d/6423.misc
@@ -0,0 +1 @@
+Clarifications for the email configuration settings.
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index 09dd21352f8f2e800d46048d3e5686754d2082f8..c7391f0c485e086ee691a3fca2ed0a37e09f1877 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -1333,8 +1333,23 @@ password_config:
 #   smtp_user: "exampleusername"
 #   smtp_pass: "examplepassword"
 #   require_transport_security: false
+#
+#   # notif_from defines the "From" address to use when sending emails.
+#   # It must be set if email sending is enabled.
+#   #
+#   # The placeholder '%(app)s' will be replaced by the application name,
+#   # which is normally 'app_name' (below), but may be overridden by the
+#   # Matrix client application.
+#   #
+#   # Note that the placeholder must be written '%(app)s', including the
+#   # trailing 's'.
+#   #
 #   notif_from: "Your Friendly %(app)s homeserver <noreply@example.com>"
-#   app_name: Matrix
+#
+#   # app_name defines the default value for '%(app)s' in notif_from. It
+#   # defaults to 'Matrix'.
+#   #
+#   #app_name: my_branded_matrix_server
 #
 #   # Enable email notifications by default
 #   #
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index ac1724045f0468b45ce0d1ce1face7a3626497f5..18f42a87f95219868c0f5c3293777c9c806c5abd 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -307,8 +307,23 @@ class EmailConfig(Config):
         #   smtp_user: "exampleusername"
         #   smtp_pass: "examplepassword"
         #   require_transport_security: false
+        #
+        #   # notif_from defines the "From" address to use when sending emails.
+        #   # It must be set if email sending is enabled.
+        #   #
+        #   # The placeholder '%(app)s' will be replaced by the application name,
+        #   # which is normally 'app_name' (below), but may be overridden by the
+        #   # Matrix client application.
+        #   #
+        #   # Note that the placeholder must be written '%(app)s', including the
+        #   # trailing 's'.
+        #   #
         #   notif_from: "Your Friendly %(app)s homeserver <noreply@example.com>"
-        #   app_name: Matrix
+        #
+        #   # app_name defines the default value for '%(app)s' in notif_from. It
+        #   # defaults to 'Matrix'.
+        #   #
+        #   #app_name: my_branded_matrix_server
         #
         #   # Enable email notifications by default
         #   #