What is the difference between transactional email and marketing email, and why does it matter for deliverability?

Transactional emails are triggered by a specific user action — an order confirmation after a purchase, a password reset after a request, an invoice after a transaction, an OTP after a login attempt. They are sent to individual recipients at the moment of the triggering event and contain information specific to that person and that event. Marketing emails are sent in bulk to a list of subscribers simultaneously — promotional campaigns, newsletters, re-engagement sequences and product announcements. The deliverability implication of mixing these two types is significant: if a user marks a marketing email as spam, the spam complaint affects the sending reputation of the IP address that sent it. If marketing and transactional emails share the same sending IP, your order confirmation emails will be affected by spam complaints generated by your promotional campaigns. Best practice is to send transactional and marketing emails from separate IP addresses and subdomains, which is standard on properly configured email platforms. We verify that every listed provider enforces IP separation between transactional and marketing traffic.