diff --git a/ndncert-mail.conf.sample b/ndncert-mail.conf.sample
index de7809b..feaa1b5 100644
--- a/ndncert-mail.conf.sample
+++ b/ndncert-mail.conf.sample
@@ -1,9 +1,13 @@
 [ndncert.smtp]
-SMTP_SERVER = localhost or remote smtp server
-SMTP_PORT = port number, usually one from 25 465 587
-ENCRYPT_MODE = select one from ssl/starttls/none
-SMTP_USER = leave it empty if you do not have one
-SMTP_PASSWORD = leave it empty if you do not have one
+# Address or hostname of SMTP server
+smtp_server =
+# SMTP server port number; usually 25, 465, or 587
+smtp_port =
+# One of ssl/starttls/none
+encrypt_mode =
+# Optional username and password for SMTP authentication
+#smtp_user =
+#smtp_password =
 
 [ndncert.email]
 from = NDN Certificate Robot <noreply@ndncert.named-data.net>