Previous Users Not Being Removed from Autoresponder Send List

While setting up a new site, I created (and then deleted) a dummy user a number of times. Each time, I used the same email.

Now, that same email address is subscribed to the auto-responder 16 times (i.e. once for every time I created and then deleted the dummy user during the testing phase).

I believe the autoresponder module should;

1) Remove any email address from the list if that account is deleted
2) Check the list to make sure there are not duplicate email addresses