Weird problem where a shared calendar mailbox keeps sending emails to group

So I thought this going to be a case of someone adding a "outlook rule" to auto forward emails, but it turns out meeting requests were the only type of thing sent to the box where responses were forwarded to a large distro list. Turns out the fix was to go into Outlook/Tools/Options/Delegates. Someone had added a distro in there, and all meeting reuests sent to this mailbox forced a response "accepted" mail to everyone on that disto list.