1 files changed, 5 insertions, 7 deletions
diff --git a/app/mailers/notify.rb b/app/mailers/notify.rb
index e7331d88517..826e5f96fa1 100644
--- a/app/mailers/notify.rb
+++ b/app/mailers/notify.rb
@@ -110,6 +110,10 @@ class Notify < BaseMailer
 
       headers['Reply-To'] = address
 
+      fallback_reply_message_id = "<reply-#{reply_key}@#{Gitlab.config.gitlab.host}>".freeze
+      headers['References'] ||= ''
+      headers['References'] << ' ' << fallback_reply_message_id
+
       @reply_by_email = true
     end
 
@@ -121,17 +125,11 @@ class Notify < BaseMailer
   #
   # See: mail_answer_thread
   def mail_new_thread(model, headers = {})
-    headers['Message-ID'] = message_reply_id
-    headers['In-Reply-To'] = message_id(model)
-    headers['References'] = message_id(model)
+    headers['Message-ID'] = message_id(model)
 
     mail_thread(model, headers)
   end
 
-  def message_reply_id
-    Gitlab.config.incoming_email["address"].gsub("%{key}", reply_key)
-  end
-
   # Send an email that responds to an existing conversation thread,
   # with headers suitable for grouping by thread in email clients.
   #