When using completion actions for list emails, you should keep in mind that completion actions based on email link clicks only execute once per prospect, and completion actions based on email opens will retroactively apply if added after the email send. These are important considerations because they affect how your completion actions will work and what results you will see. For example, if you want to add a prospect to a list based on a link click, you should know that the completion action will only fire the first time the prospect clicks the link, not every time. Similarly, if you want to change a prospect's score based on an email open, you should know that the completion action will apply to all prospects who opened the email, even if they opened it before you added the completion action