Anyone who unsubscribes from your newsletter will be suppressed and placed on the supressed list. This does not mean that the email address is removed or deleted from Rule, but it remains but is supressed. If it is not still blocked in the system, it means that the email address is active and can be registered again for the newsletter, for example via the website and once again receive newsletters and other communication.

1. People who have marked your email as spam in their inbox will automatically be unsubscribed immediately.
2. Some subscribers who have unsubscribed have bounced, read more about them here.
3. Another possibility is that the subscriber themselves clicked on the unsubscribe link. Or the subscriber forwarded their email to someone else who may have clicked on the link.
4. Another reason could be if the subscriber has shared the campaign publicly somewhere - then someone may have clicked on the unsubscribe link there.

If the account administrator has unsubscribed the subscriber, it will look like this in the customer view (note that it is possible to reactivate the subscriber with the button in the upper right corner):