message mail delivery must happen after the first journal is created

app/models/message_observer.rb

@@ -16,7 +16,10 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 class MessageObserver < ActiveRecord::Observer
-  def after_create(message)
-    Mailer.deliver_message_posted(message) if Setting.notified_events.include?('message_posted')
+  def after_save(message)
+    if message.last_journal.version == 1
+      # Only deliver mails for the first journal
+      Mailer.deliver_message_posted(message) if Setting.notified_events.include?('message_posted')
+    end
   end
 end