HVE and ECS are two competing Microsoft Cloud Email Services. At least, they seem to compete. In reality, HVE and ECS serve different target audiences. HVE is all about internal email services for apps and devices while ECS is for high volume external mailings like customer newsletters. We tested both services by sending subscription reminder notifications to Office 365 for IT Pros readers.
https://office365itpros.com/2024/08/13/microsoft-cloud-email-services/