Transactional email
One-to-one email triggered by user action.
Transactional email is sent in response to a user-initiated action: password reset, receipt, magic link, account verification. Volume is unpredictable, latency matters, and missed delivery is a product failure. It contrasts with marketing email, which is one-to-many and sent on the senders schedule.
reading this as teams building autonomous agents
An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.
Applied to transactional email, that means weighing inbound parsing, idempotency keys, webhook coverage, and operating track record ahead of the rest, against inbound parsing into tool calls and model-generated sends that must not duplicate.