Recipient not in this inbox

message.recipient_invalid · HTTP 400

What it means

An address given in to is not an address of the inbox the message was injected into, so nothing was stored. An inbox takes any local part under its own domain; an inbox created before inboxes had their own domain takes only its address. Another inbox's address, another domain and the bare receiving domain are refused. The problem's recipient field names the address.

What to do

Use addresses under the inbox's domain (see its domain and address in GET /v1/inboxes/{id}), or leave out to to use the message's own To, Cc and Bcc addresses under the inbox.

Every error the API returns is a JSON problem (RFC 9457) whose code names it and whose type links to its page here. See the docs for how the API works.