curl --request POST \
  --url https://api.example.com/api/Messages/Preview \
  --header 'Content-Type: application/json' \
  --data '
{
  "subject": "<string>",
  "body": "<string>",
  "jobId": 123,
  "placementId": 123,
  "changeRequestId": 123,
  "recipientEntityId": 1,
  "recipientRecordId": 123
}
'

{
  "subject": "<string>",
  "body": "<string>",
  "jobId": 123,
  "placementId": 123,
  "changeRequestId": 123,
  "recipientEntityId": 1,
  "recipientRecordId": 123
}