I want to automatically delete any mail I receive from anyone at addr.com
(which I believe has been selling my e-mail address for years, ever since I
used them as my webhost). I have tried making a rule which says "delete any
mail which has "@addr.com" in the sender's address", but I'm still getting
mail from them and people associated with them.

I also tried "addr.com" and "*@addr.com"  but I'm still getting mail.

I think Outlook should allow the use of an asterisk as a wildcard.