This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:24dc401b-1d15-4232-b730-a31dd5e6c4a0

Content

The server... MUST utilize the addressing originally stored on the bto / bcc properties for determining recipients in delivery.

Origin

prefix The server MUST remove the bto and/or bcc properties, if they exist, from the ActivityStreams object before delivery, but

MUST utilize the addressing originally stored on the bto / bcc properties for determining recipients in delivery.
 
suffix The server MUST then add this new Activity to the outbox collection.

https://www.w3.org/TR/activitypub/

JSON

{
  "id": "urn:uuid:24dc401b-1d15-4232-b730-a31dd5e6c4a0",
  "uuid": "24dc401b-1d15-4232-b730-a31dd5e6c4a0",
  "type": "Behavior",
  "content": "The server... MUST utilize the addressing originally stored on the bto / bcc properties for determining recipients in delivery.\n",
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "Client to server interaction"
    },
    {
      "name": "server delivering activities clients post to an actor's outbox"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#x6-client-to-server-interactions",
      "branch": [
        6
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "The server MUST remove the bto and/or bcc properties, if they exist, from the ActivityStreams object before delivery, but \n",
      "exact": "MUST utilize the addressing originally stored on the bto / bcc properties for determining recipients in delivery.\n",
      "suffix": "The server MUST then add this new Activity to the outbox collection.\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}