config/environments/production.rb

@@ -107,6 +107,9 @@ Rails.application.configure do
     }
   end
 
+  # enable SMTPS: SMTP over direct TLS connection
+  ActionMailer::Base.smtp_settings[:tls] = true if ENV['SMTP_TLS'].present? && ENV['SMTP_TLS'] != "false"
+
   # If configured to 'none' don't check the smtp servers certificate
   ActionMailer::Base.smtp_settings[:openssl_verify_mode] =
     ENV['SMTP_OPENSSL_VERIFY_MODE'] if ENV['SMTP_OPENSSL_VERIFY_MODE'].present?

sample.env

@@ -135,6 +135,9 @@ GOOGLE_ANALYTICS_TRACKING_ID=
 #   SMTP_AUTH=plain
 #   SMTP_STARTTLS_AUTO=true
 #
+#   enable SMTPS: SMTP over direct TLS connection; usually port 465
+#   SMTP_TLS=true
+#
 # If your mail server has a self-signed certificate, you'll also need to include the line below.
 # Please note that enable this presents its own security risks and should not be done unless necessary.
 #   SMTP_OPENSSL_VERIFY_MODE=none