diff --git a/.env.production.sample b/.env.production.sample
index 6555cb12a2e..0759ed7faf5 100644
--- a/.env.production.sample
+++ b/.env.production.sample
@@ -35,6 +35,8 @@ 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
 SMTP_SERVER=smtp.mailgun.org
 SMTP_PORT=587
 SMTP_LOGIN=
diff --git a/config/environments/production.rb b/config/environments/production.rb
index 80021287a52..a4cdb273232 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -100,8 +100,10 @@ Rails.application.configure do
     :address              => ENV['SMTP_SERVER'],
     :user_name            => ENV['SMTP_LOGIN'],
     :password             => ENV['SMTP_PASSWORD'],
+
     :domain               => ENV['SMTP_DOMAIN'] || ENV['LOCAL_DOMAIN'],
-    :authentication       => ENV['SMTP_AUTH_METHOD'] || :plain,
+    :authentication       => ENV['SMTP_AUTH_METHOD'] == 'none' ? nil : ENV['SMTP_AUTH_METHOD'] || :plain,
+
     :openssl_verify_mode  => ENV['SMTP_OPENSSL_VERIFY_MODE'],
     :enable_starttls_auto => ENV['SMTP_ENABLE_STARTTLS_AUTO'] || true,
   }