FIX: Do not validate messages sent to mailing list mirror

spec/components/email/receiver_spec.rb

@@ -818,6 +818,16 @@ describe Email::Receiver do
       expect { process(:mailinglist_reply) }.to change { topic.posts.count }
     end
 
+    it "should skip validations for staged users" do
+      Fabricate(:user, email: "alice@foo.com", staged: true)
+      expect { process(:mailinglist_short_message) }.to change { Topic.count }
+    end
+
+    it "should skip validations for regular users" do
+      Fabricate(:user, email: "alice@foo.com")
+      expect { process(:mailinglist_short_message) }.to change { Topic.count }
+    end
+
     context "read-only category" do
       before do
         category.set_permissions(everyone: :readonly)

spec/fixtures/emails/mailinglist_short_message.eml

@@ -0,0 +1,12 @@
+From: alice@foo.com
+To: list@example.com
+Subject: test
+Date: Mon, 16 Oct 2017 09:18:32 +0100
+Message-ID: <bddaa334ef93b5f3c7c3a42599330844@foo.com>
+Precedence: list
+List-Id: Example List <list@example.com>
+Content-Transfer-Encoding: 7bit
+Content-Type: text/plain; charset="us-ascii"
+Sender: list-bounces@example.com
+
+Hello world!