suppress rejection email when email was sent to mailinglist mirror category

lib/email/processor.rb

@@ -13,17 +13,17 @@ module Email
 
     def process!
       begin
-        receiver = Email::Receiver.new(@mail)
-        receiver.process!
+        @receiver = Email::Receiver.new(@mail)
+        @receiver.process!
       rescue RateLimiter::LimitExceeded
         @retry_on_rate_limit ? Jobs.enqueue(:process_email, mail: @mail) : raise
       rescue Email::Receiver::BouncedEmailError => e
         # never reply to bounced emails
         log_email_process_failure(@mail, e)
-        set_incoming_email_rejection_message(receiver.incoming_email, I18n.t("emails.incoming.errors.bounced_email_error"))
+        set_incoming_email_rejection_message(@receiver.incoming_email, I18n.t("emails.incoming.errors.bounced_email_error"))
       rescue => e
         log_email_process_failure(@mail, e)
-        incoming_email = receiver.try(:incoming_email)
+        incoming_email = @receiver.try(:incoming_email)
         rejection_message = handle_failure(@mail, e)
         if rejection_message.present?
           set_incoming_email_rejection_message(incoming_email, rejection_message.body.to_s)
@@ -94,6 +94,7 @@ module Email
     end
 
     def can_send_rejection_email?(email, type)
+      return false if @receiver.sent_to_mailinglist_mirror?
       return true if type == :email_reject_unrecognized_error
 
       key = "rejection_email:#{email}:#{type}:#{Date.today}"

spec/components/email/processor_spec.rb

@@ -87,4 +87,22 @@ describe Email::Processor do
 
   end
 
+  context "mailinglist mirror" do
+    before do
+      SiteSetting.email_in = true
+      Fabricate(:mailinglist_mirror_category)
+    end
+
+    it "does not send rejection email" do
+      Email::Receiver.any_instance.stubs(:process_internal).raises("boom")
+
+      email = <<~EMAIL
+        From: foo@example.com
+        To: list@example.com
+        Subject: Hello world
+      EMAIL
+
+      expect { Email::Processor.process!(email) }.to_not change { EmailLog.count }
+    end
+  end
 end

spec/fabricators/category_fabricator.rb

@@ -29,3 +29,9 @@ end
 Fabricator(:link_category, from: :category) do
   before_validation { |category, transients| category.topic_featured_link_allowed = true }
 end
+
+Fabricator(:mailinglist_mirror_category, from: :category) do
+  email_in 'list@example.com'
+  email_in_allow_strangers true
+  mailinglist_mirror true
+end