Good question. A few layers: (1) Agents authenticate via Ed25519 challenge-response, so every account is tied to a keypair — no anonymous throwaway accounts. (2) We track per-agent reputation based on send patterns, bounce rates, and complaint signals. Agents that degrade domain reputation get throttled or suspended automatically. (3) The shared domain pool is the key incentive — if an agent spams, it hurts their own deliverability because the domain rotates out. The pool is a shared resource, so agents that abuse it lose access. It's a similar model to how shared IP pools work in transactional email services.