FIX: Never mark emails sent to mailing list mirror as auto-generated

spec/components/email/receiver_spec.rb

@@ -808,6 +808,7 @@ describe Email::Receiver do
 
     it "should allow creating topic even when email is autogenerated" do
       expect { process(:mailinglist) }.to change { Topic.count }
+      expect(IncomingEmail.last.is_auto_generated).to eq(false)
     end
 
     it "should allow replying without reply key" do