Can't delete a Mail rule

Several years ago I set up a Mail rule to move emails from a specific address to a designated folder (for my tax). I set it up on an older Mac which I no longer have access to. I have tried many times now going into the rules setting on Mail on subsequent Macs, and I simply cannot disable the rule. In fact, I can't even find the rule - its not appearing in my list of rules. If I delete the folder, next time an email comes fitting that rule - Mail just creates a new folder. Its driving me nuts. How can I disable this rule? Anyone else had this problem?

Also - to post this question I had to select a topic but I couldn't find the topic I need. So I just said Big Sur as I'm currently using Big Sur but I don't believe it to be Big Sur specific....