At the startup I work for, there's 2-3 "true" lists of emails, spread between 2-3 different email-like SaaS products which all have their own unsubscribe management system.<p>Users who unsubscribe in one system stay subscribed in other systems, inevitably leading to frustration.<p>How do you keep track of who unsubscribed to your emails?
Ideally, use one email marketing system. For example, Mailchimp lets us know exactly which customers have unsubscribed from certain types of emails for a selected list.