Shared IP
A sending IP used by many customers of a provider.
Most senders start on a shared IP pool. Reputation is collective: one bad sender can drag the pool down, but established providers actively manage their pools. Below 100k/month, shared IPs are usually preferable to dedicated.
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 shared ip, 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.