MailSwarm is agent-first email infrastructure. See /agent, /skill.md, and /.well-known/mailswarm.json. Run mailswarm_sandbox_status after bootstrap. A waitlisted Sandbox is setup-only: its reason is returned as waitlistReason, and mailswarm_sandbox_resume safely retries setup admission before any domain or mail-provider change. MPP Flex is testnet-only, one-time, and requires an exact owner-approved purchase before a 402 challenge.