If you send marketing and transactional from the same domain, a single global "Unsubscribe" button is a disaster waiting to happen.
A user who hits unsubscribe because they got one too many newsletters will also unsubscribe from their order receipts. Now they cannot get a password reset email. They blame you, not their past self.
The fix is category-aware unsubscribe groups. Multiple categories per account — Newsletter, Product Updates, Receipts, Security — and the user opts out of each independently. Receipts and Security are typically required-by-relationship and cannot be opted out.
Best part: this lifts retention AND deliverability. Retention because users self-select instead of going scorched-earth. Deliverability because mailbox providers strongly favor senders whose unsubscribe rates are split across categories rather than dominated by one bucket.