Added `In-Reply-To` and `References` email headers. Additionally removed username from

email replies and new posts to keep the subjects collapsable.

config/locales/server.en.yml

@@ -934,7 +934,7 @@ en:
         Please visit this link to view the topic: %{base_url}%{url}
 
     user_replied:
-      subject_template: "[%{site_name}] %{username} replied to your post in '%{topic_title}'"
+      subject_template: "[%{site_name}] new reply to your post in '%{topic_title}'"
       text_body_template: |
         %{username} replied to your post in '%{topic_title}' on %{site_name}:
 
@@ -967,7 +967,7 @@ en:
         %{respond_instructions}
 
     user_posted:
-      subject_template: "[%{site_name}] %{username} posted in '%{topic_title}'"
+      subject_template: "[%{site_name}] new post in '%{topic_title}'"
       text_body_template: |
         %{username} posted in '%{topic_title}' on %{site_name}:
 

lib/email/sender.rb

@@ -47,11 +47,24 @@ module Email
                                user_id: @user.try(:id))
 
 
-      @message.header['List-Id'] = Email::Sender.list_id_for(SiteSetting.title, Discourse.base_url)
+      host = Email::Sender.host_for(Discourse.base_url)
 
-      add_header_to_log('X-Discourse-Reply-Key', email_log, :reply_key)
-      add_header_to_log('X-Discourse-Post-Id', email_log, :post_id)
-      add_header_to_log('X-Discourse-Topic-Id', email_log, :topic_id)
+      @message.header['List-Id'] = Email::Sender.list_id_for(SiteSetting.title, host)
+
+      topic_id = header_value('X-Discourse-Topic-Id')
+      post_id = header_value('X-Discourse-Post-Id')
+      reply_key = header_value('X-Discourse-Reply-Key')
+
+      if topic_id.present?
+        email_log.topic_id = topic_id
+
+        topic_identitfier = "<topic/#{topic_id}@#{host}>"
+        @message.header['In-Reply-To'] = topic_identitfier
+        @message.header['References'] = topic_identitfier
+      end
+
+      email_log.post_id = post_id if post_id.present?
+      email_log.reply_key = reply_key if reply_key.present?
 
       # Remove headers we don't need anymore
       @message.header['X-Discourse-Topic-Id'] = nil
@@ -66,8 +79,7 @@ module Email
 
     end
 
-    def self.list_id_for(site_name, base_url)
-
+    def self.host_for(base_url)
       host = "localhost"
       if base_url.present?
         begin
@@ -76,18 +88,19 @@ module Email
         rescue URI::InvalidURIError
         end
       end
+      host
+    end
 
+    def self.list_id_for(site_name, host)
       "\"#{site_name.gsub(/\"/, "'")}\" <discourse.forum.#{Slug.for(site_name)}.#{host}>"
     end
 
     private
 
-    def add_header_to_log(name, email_log, email_log_field)
+    def header_value(name)
       header = @message.header[name]
-      return unless header
-
-      val = header.value
-      email_log[email_log_field] = val if val.present?
+      return nil unless header
+      header.value
     end
 
   end

spec/components/email/sender_spec.rb

@@ -20,32 +20,37 @@ describe Email::Sender do
     Email::Sender.new(message, :hello).send
   end
 
+  context "host_for" do
+    it "defaults to localhost" do
+      Email::Sender.host_for(nil).should == "localhost"
+    end
+
+    it "returns localhost for a weird host" do
+      Email::Sender.host_for("this is not a real host").should == "localhost"
+    end
+
+    it "parses hosts from urls" do
+      Email::Sender.host_for("http://meta.discourse.org").should == "meta.discourse.org"
+    end
+
+    it "downcases hosts" do
+      Email::Sender.host_for("http://ForumSite.com").should == "forumsite.com"
+    end
+
+  end
+
   context "list_id_for" do
-
     it "joins the host and forum name" do
-      Email::Sender.list_id_for("myforum", "http://mysite.com").should == '"myforum" <discourse.forum.myforum.mysite.com>'
-    end
-
-    it "uses localhost when no host is present" do
-      Email::Sender.list_id_for("myforum", nil).should == '"myforum" <discourse.forum.myforum.localhost>'
-    end
-
-    it "uses localhost with a weird host" do
-      Email::Sender.list_id_for("Fun", "this is not a real host").should == '"Fun" <discourse.forum.fun.localhost>'
+      Email::Sender.list_id_for("myforum", "mysite.com").should == '"myforum" <discourse.forum.myforum.mysite.com>'
     end
 
     it "removes double quotes from names" do
-      Email::Sender.list_id_for('Quoted "Forum"', 'http://quoted.com').should == '"Quoted \'Forum\'" <discourse.forum.quoted-forum.quoted.com>'
+      Email::Sender.list_id_for('Quoted "Forum"', 'quoted.com').should == '"Quoted \'Forum\'" <discourse.forum.quoted-forum.quoted.com>'
     end
 
     it "converts the site name to lower case and removes spaces" do
-      Email::Sender.list_id_for("Robin's cool Forum!", "http://robin.com").should == '"Robin\'s cool Forum!" <discourse.forum.robins-cool-forum.robin.com>'
+      Email::Sender.list_id_for("Robin's cool Forum!", "robin.com").should == '"Robin\'s cool Forum!" <discourse.forum.robins-cool-forum.robin.com>'
     end
-
-    it "downcases host names" do
-      Email::Sender.list_id_for("cool", "http://ForumSite.com").should == '"cool" <discourse.forum.cool.forumsite.com>'
-    end
-
   end
 
   context 'with a valid message' do
@@ -92,6 +97,9 @@ describe Email::Sender do
       When { email_sender.send }
       Then { expect(email_log.post_id).to eq(3344) }
       Then { expect(email_log.topic_id).to eq(5577) }
+      Then { expect(message.header['In-Reply-To']).to be_present }
+      Then { expect(message.header['References']).to be_present }
+
     end
 
     context "email log with a reply key" do