To start with I would check to see if the same email is being sent our multiple times or if it's actually creating three identical emails.
If you have a look in the tps_user_message and tps_user_message_recipient table in the database, you will be able to see the message. Is there only one message in here that matches the one you are getting? If so, it could be that the email isn't set to be sent. If this is the case, you should be able to see an error message in your event log for the outbound mail services.
If you do have multiple emails in these tables for the same report, then I would suggest checking if there is any problem with scheduled bulk action itself.