What is transactional email?

Transactional email is system-generated mail triggered by a specific user action or system event, rather than sent as part of a scheduled marketing campaign. Examples: password reset emails, signup confirmation emails, order receipts, shipping notifications, payment receipts, account alerts.

Key differences from marketing email:

• One recipient per send rather than thousands.
• Triggered by an event (form submission, purchase, API call) rather than scheduled.
• Higher engagement because recipients usually expect the message and want it (they just clicked "Forgot password").
• Lower complaint rates for the same reason.
• Often legally exempt from many marketing-email regulations (CAN-SPAM, etc.) because they relate to an existing business relationship.
• Stricter deliverability requirements. A late or missing transactional email (password reset, order confirmation) creates customer-experience problems immediately.

Most senders use a separate ESP, or at least a separate ESP-account or sending IP, for transactional vs. marketing. Mixing them on the same IP risks marketing-driven reputation damage breaking transactional delivery, which has real business consequences.

Common transactional-focused ESPs: SendGrid, Mailgun, Postmark, Amazon SES, Mailjet.