I have enabled system cron and every time cron runs it is sending reminder for "Topic moderation notification" for the same topic even after topic has been moderated. Then deleted the topic and still got the message. Also get repeated email subscription to a post. This also happens after the post has been deleted! And this did not go away after clearing cache on the system menu. Finally after clearing cache by deleting the files in the cache folder the emails stopped.
I tried again with another moderation and post and it had the same effect.