Transactional emails confirm specific user actions (order confirmation, password reset, invoice) and don't require opt-in consent under most laws. Marketing emails promote products/services and require explicit consent under GDPR, CASL, and DPDP. The distinction matters legally and deliverability-wise — transactional emails have higher open rates and should be sent from a separate IP to protect marketing reputation. MisarMail supports separate sending streams for transactional and marketing email.