curl --request POST \
  --url https://your-instance.example.com/api/email/messages/send \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "accountId": "<string>",
  "to": "<string>",
  "body": "<string>",
  "cc": [
    "<string>"
  ],
  "bcc": [
    "<string>"
  ],
  "subject": "<string>",
  "isHtml": true,
  "threadId": "<string>",
  "inReplyTo": "<string>",
  "references": "<string>",
  "isInternal": true,
  "attachments": [
    {
      "storageKey": "<string>",
      "url": "<string>",
      "filename": "<string>",
      "contentType": "<string>",
      "size": 123
    }
  ]
}
'

{}