In your case the setup has to be a little different because your list manager link uses a kind of redirect that makes impossible to get the referrer information that you need, so the "list-manage" will not be on the referrer and the bucket will not be filled.
However you use Google Analytics and the landing page of the link you provided have the "utm_medium=email" in the url, so you could change the setup to use the "visited a page" behavior where the url contains utm_medium=email, that way you'll be able to bucket users that are email subscribers because they will have the utm_medium everytime they are redirected by your list manager.
Please let me know if you have more questions
BTBuckets Team
BTBuckets have a nice feature called overwrite buckets. In the bucket setup, where you configure the bucket name, etc, you can set to overwrite one or more buckets, that means, in your case, when the user enters the email subscribers bucket, BTBuckets will remove him/her from the selected buckets and he/she will be only on that bucket so you'll be able to target them properly as you want :-)
Please let me know if you have more questions
BTBuckets Team
Okay, one more question - do the default buckets overwrite? Or do I need to recreate them and enable this? Goal is never to pop a message to a visitor that we know has been there before.
BTBuckets is flexible :-), setup or edit a bucket and select it on the buckets list to overwrite, for example, for those email subscribers you can check the return visitor bucket, as soon they enter the subscribers bucket, they will be removed from the return visitor bucket.
Please let me know if you have more questions
BTBuckets Team