Delegate rule that won't go away

[Joe]

I have a problem where one of our users added a distibution list as a
delelgate, (in tools, options deligates). When she sent out an invitation to
one person, and that person responded, everyone in that distribution list
received the accepted notice. So, we figured when we remove the DL from the
delelgates field, the problem would go away. Well, it won't go away, and
now, everytime she sends out an invitation, whoever responds, that DL will
still get the acceptance notice.
How can we get this to stop?

Thanks,

Joe