Add second SMTP setting

app/mailers/application_mailer.rb

@@ -13,4 +13,30 @@ class ApplicationMailer < ActionMailer::Base
       yield
     end
   end
+
+  class DynamicSettingsInterceptor
+    class << self
+      def delivering_email(message)
+        set_second_delivery_options(message) if use_second?(message)
+      end
+
+      private
+
+      def use_second?(message)
+        return unless Rails.configuration.x.second_smtp_settings[:address]
+    
+        Rails.configuration.x.domains_to_use_second_smtp&.any? { |domain| recipient_domains(message).include?(domain) }
+      end
+    
+      def recipient_domains(message)
+        message.recipients_addresses.map(&:domain).compact
+      end
+    
+      def set_second_delivery_options(message)
+        message.delivery_method.settings.merge!(Rails.configuration.x.second_smtp_settings)
+      end
+    end
+  end
+
+  register_interceptor DynamicSettingsInterceptor
 end

config/environments/production.rb

@@ -112,6 +112,22 @@ Rails.application.configure do
     :ssl                  => ENV['SMTP_SSL'].presence,
   }
 
+  config.x.second_smtp_settings = {
+    :port                 => ENV['SECOND_SMTP_PORT'],
+    :address              => ENV['SECOND_SMTP_SERVER'],
+    :user_name            => ENV['SECOND_SMTP_LOGIN'].presence,
+    :password             => ENV['SECOND_SMTP_PASSWORD'].presence,
+    :domain               => ENV['SECOND_SMTP_DOMAIN'] || ENV['LOCAL_DOMAIN'],
+    :authentication       => ENV['SECOND_SMTP_AUTH_METHOD'] == 'none' ? nil : ENV['SMTP_AUTH_METHOD'] || :plain,
+    :ca_file              => ENV['SECOND_SMTP_CA_FILE'].presence,
+    :openssl_verify_mode  => ENV['SECOND_SMTP_OPENSSL_VERIFY_MODE'],
+    :enable_starttls_auto => ENV['SECOND_SMTP_ENABLE_STARTTLS_AUTO'] || true,
+    :tls                  => ENV['SECOND_SMTP_TLS'].presence,
+    :ssl                  => ENV['SECOND_SMTP_SSL'].presence,
+  }
+
+  config.x.domains_to_use_second_smtp = ENV.fetch('DOMAINS_TO_USE_SECOND_SMTP', '').parse_csv&.map(&:strip)
+
   config.action_mailer.delivery_method = ENV.fetch('SMTP_DELIVERY_METHOD', 'smtp').to_sym
 
   config.action_dispatch.default_headers = {