Inbox placement
Whether delivered email lands in the inbox instead of spam.
Delivery only means the receiving server accepted the message. Inbox placement asks where the message landed after filtering. Seed-list tests and panel data can estimate placement, but no test perfectly represents every recipient inbox.
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 inbox placement, 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.