Resubscribe a contact who opted out of marketing email

Short answer

HubSpot's KB says you can manually resubscribe an opted-out contact if you provide a legal basis and explanation. The Manage communication subscription workflow action cannot resubscribe contacts who opted out themselves, only ones unsubscribed by your team. Opted-out contacts still get one-to-one and transactional emails. The Resubscription email setting lets unsubscribed contacts opt themselves back in.