Updated note about 'none' SMTP authentication method in .env.production.sample (#2167)

.env.production.sample

@@ -36,7 +36,8 @@ OTP_SECRET=
 # E-mail configuration
 # Note: Mailgun and SparkPost (https://sparkpo.st/smtp) each have good free tiers
 # If you want to use an SMTP server without authentication (e.g local Postfix relay)
-# then set SMTP_AUTH_METHOD to 'none' and leave SMTP_LOGIN and SMTP_PASSWORD blank
+# then set SMTP_AUTH_METHOD to 'none' and *comment* SMTP_LOGIN and SMTP_PASSWORD.
+# Leaving them blank is not enough for authentication method 'none'.
 SMTP_SERVER=smtp.mailgun.org
 SMTP_PORT=587
 SMTP_LOGIN=