app/mailers/application_mailer.rb

@@ -3,16 +3,6 @@
 # frozen_string_literal: true
 
 class ApplicationMailer < ActionMailer::Base
-  class << self
+  default from: 'from@example.com'
-    private
-
-    def default_from
-      File.read('/run/secrets/smtp_user_name').strip
-    rescue Errno::ENOENT
-      'development@example.com'
-    end
-  end
-
-  default from: default_from
   layout 'mailer'
 end

config/environments/production.rb

@@ -79,8 +79,7 @@ Rails.application.configure do
       port: File.read("/run/secrets/smtp_port").strip.to_i,
       user_name: File.read("/run/secrets/smtp_user_name").strip,
       password: File.read("/run/secrets/smtp_password").strip,
-      authentication: File.read("/run/secrets/smtp_authentication").strip.to_sym,
+      authentication: File.read("/run/secrets/smtp_authentication").strip.to_sym
-      tls: true
     }
   rescue Errno::ENOENT
     {}