synapse-product/docs/admin_api/server_notices.md

Server Notices

The API to send notices is as follows:

POST /_synapse/admin/v1/send_server_notice

or:

PUT /_synapse/admin/v1/send_server_notice/{txnId}

You will need to authenticate with an access token for an admin user.

When using the PUT form, retransmissions with the same transaction ID will be ignored in the same way as with PUT /_matrix/client/r0/rooms/{roomId}/send/{eventType}/{txnId}.

The request body should look something like the following:

{
    "user_id": "@target_user:server_name",
    "content": {
        "msgtype": "m.text",
        "body": "This is my message"
    }
}

You can optionally include the following additional parameters:

• type: the type of event. Defaults to m.room.message.
• state_key: Setting this will result in a state event being sent.

Once the notice has been sent, the API will return the following response:

{
    "event_id": "<event_id>"
}

Note that server notices must be enabled in homeserver.yaml before this API can be used. See server_notices.md for more information.