A transactional email is a message triggered by something a person did or by an event in their account, and sent to that person alone. Order confirmations, invoices, shipping updates, OTPs, password resets, booking confirmations and account alerts are all transactional. The recipient expects them and often needs them to complete a task.
Because they are expected and important, transactional emails behave differently from marketing. They need to arrive within seconds: an OTP that takes three minutes is a failed login. They are usually sent through an API or SMTP connection from your website or app, rather than designed and scheduled in a campaign editor. And they generally get high engagement, which is good for your sender reputation.
Keep transactional and marketing traffic separate where you can, for example with a different subdomain, sending stream or IP. If a marketing campaign causes complaints, you don’t want password resets to be delayed or filtered as a result. Many businesses use a subdomain such as notify.yourbrand.com for transactional mail and news.yourbrand.com for marketing.
The line between the two matters legally. Transactional messages generally don’t require marketing consent and don’t need an unsubscribe link, but they must stay transactional. Adding a large promotional section to an order confirmation can turn it into a marketing message in the eyes of regulators and mailbox providers. A small, relevant mention is usually fine; a sale banner is not.
A Mumbai food delivery app sends order confirmations through an email API the moment payment succeeds, with a delivery log showing each message was accepted within a couple of seconds. Weekly offers go out separately as marketing campaigns, only to customers who opted in.
MailNesto sends transactional email such as receipts and OTPs through its API from the same account as your campaigns, with a delivery log, tags for each message type and optional open and click tracking.