Hi, I'm struggling to understand how to setup a standard Monthly Newsletter. Let's say I use a form for people to sign-up for it. In order to send them the newsletter in a journey, they must be part of a segment. But - subscription centers only use Marketing Lists. Does this mean that when they sign up for a monthly newsletter, I need to add them to both a segment and a Marketing List? And if they unsubscribe, I need to remove them from both?