On a dev site, I’ve installed the most recent version of the plugin (4.0.2), and have set it for double opt-in. When I enter an email address in the subscribe field, the welcome message is sent out, with a link to confirm the subscription in the message. The email address appears in the Audience list as subscribed, and a new post published generates a notification to the address even before the confirmation link is clicked. After the confirmation link is clicked, the appropriate welcome message is displayed and welcome email sent out, with an unsubscribe link included.

When the unsubscribe link is clicked, the appropriate ‘your unsubscribed’ message is displayed, and the email address shows in the Audience list as unsubscribed. But posts published after that still generate notification emails to the email address.

So, neither the double opt-in nor the unsubscribe functions appear to be working.