FIX: Don't reply to Unsubscribe email sent to mailing list mirror

lib/email/receiver.rb

@@ -838,6 +838,8 @@ module Email
 
     def subscription_action_for(body, subject)
       return unless SiteSetting.unsubscribe_via_email
+      return if sent_to_mailinglist_mirror?
+
       if ([subject, body].compact.map(&:to_s).map(&:downcase) & ['unsubscribe']).any?
         :confirm_unsubscribe
       end

spec/components/email/receiver_spec.rb

@@ -1103,6 +1103,13 @@ describe Email::Receiver do
         expect { process(:mailinglist_reply) }.to change { topic.posts.count }
       end
     end
+
+    it "ignores unsubscribe email" do
+      SiteSetting.unsubscribe_via_email = true
+      Fabricate(:user, email: "alice@foo.com")
+
+      expect { process("mailinglist_unsubscribe") }.to_not change { ActionMailer::Base.deliveries.count }
+    end
   end
 
   it "tries to fix unparsable email addresses in To and CC headers" do

spec/fixtures/emails/mailinglist_unsubscribe.eml

@@ -0,0 +1,11 @@
+Return-Path: <discourse@bar.com>
+From: alice@foo.com
+To: list@example.com
+Date: Thu, 13 Jun 2013 17:03:48 -0400
+Message-ID: <56@foo.bar.mail>
+Subject: UnSuBScRiBe
+Mime-Version: 1.0
+Content-Type: text/plain;
+Content-Transfer-Encoding: 7bit
+
+I've basically had enough of your mailing list and would very much like it if you went away.