The job to be done
Marketing automation has one honest purpose in a sales-led business: make sure the right message reaches the right contact at the right moment without a person having to remember to send it. Everything else, the dashboards and the funnels and the scoring models, exists to serve that.
The measure of success is therefore not how many emails were delivered. It is whether the sales team received better-timed conversations than they would have had otherwise. A flow that sends beautifully and produces no calls has failed.