Under Admin->Production->Message Center -> Default ->Deliveries
On first look, we have all the deliveries send out using Message Center. Schema name is same nms:delivery . I think @retryCount column must be having the details you looking for. Do let me know if this works for you.
Thanks, Kapil. I had checked that field thinking the same, but doesn't look like it's getting populated in our instance. Figured it may be recorded in another table