ErrorIrresolvableConflict — Edit conflict

A conflict occurred because the item changed (e.g., updated or deleted by someone else). If you were updating an item via Riposte and got this 409 error, it means your copy is stale. Use a GET operation (e.g., /accounts/{accountId}/messages/{messageId} or equivalent) to fetch the latest version of the item. Then apply your changes again, possibly using an If-Match header if Riposte supports it, or just ensuring no concurrent changes.