Switch the instant inbox on, or create a named mailbox on it (<agent>@<code>.oveyon.app)

No DNS on your side: the domain is ours. Without localPart it switches the account inbox on — its domain and the catch-all *@<code>.oveyon.app — and returns the catch-all (201 the first time, 200 after: idempotent). With localPart it creates a named mailbox with its own channels and policies (201), like POST /v1/inbound/routes — the same limits (200 mailboxes per domain, 1000 per account), the same inline webhook (secret shown once), born without security choices. Received mail counts like any inbound mail; above the per-hour limit the MX answers 450 4.2.1 and the sender retries. Sending FROM it is for paid plans only: on the free plan /v1/send and /v1/inbound/{uid}/reply answer 422 managed_domain_requires_paid_plan (SMTP: 550 5.7.1). Forwarding from it follows the forwarding rules of every mailbox (verified destinations only). While the instant inbox is not enabled on the platform this route answers 404 not_found. Scope write:inbound.