I installed the OpenEBS application from the marketplace onto a Kubernetes cluster. Following the instructions from MayaData (https://help.mayadata.io/hc/en-us/articles/360033033312-OpenEBS-on-DigitalOcean-Marketplace...
DigitalOcean Managed Kubernetes
I have a Kubernetes cluster that uses nginx for handling inbound requests behind a DigitalOcean load balancer. Here's what an inbound SMTP request (port 25) goes through to get to my Postfix server:
DO Load Balancer