How do visitors choose which emails they get from my website?

Open your website in Website Builder, then Config, Email List, and add rows under Email Topics: pick one of your lists for each, type the name visitors see (for example Auction Watch) and one line about it, and drag the rows into order. Make the lists first in Email Campaigns, Lists.

The website's Join pop-up then signs visitors up for every topic, with the checkboxes folded under one small line below the email field (Subscribe to All newsletters) so a visitor can untick what they do not want. One sign-up covers every email. An Email Signup block shows its heading, its text and one button that opens the same pop-up with the block's list ticked. The block has no email field of its own, so there is only ever one way to sign up. A signed-in member sees a Get these emails button instead.

Members turn each topic on or off on their member page under Your emails. Everyone who signs up is in your Contacts with the lists they chose, so you can send a campaign to one topic.