Dear Margot--
What worked to unsubscribe another mail account was a link at the TOP of the QuickTopic page: beside the 'Subscribe' button is a small "to get & post, or stop messages by email," with a small envelope icon. I clicked that icon & followed the steps to unsubscribe.

Meanwhile, I'll look to see if there's a way I as administrator can kill this list dead once & for all. More apologies,

b