A message were delivered separately from different ESS servers to multiple recipients

Products

• Email Security.cloud

Issue/Introduction

When a message has multiple recipients, it looked it was delivered separately from different ESS servers (different IP addresses). Those recipients have different domain name, but all domains are registered to ESS with the same Inbound route. Why they were delivered from different ESS servers? Does it work by design? If the recipients have the same domain, will they be sent out from the same ESS server (1 ESS server)?

Environment

Email Security.cloud

Resolution

This works by design. When the message with multiple recipients is delivered through ESS backend mail server (MTA), the message will be delivered to each recipient from different servers. This behavior does not depend on the recipient's domain address. Even through the recipients have the same domain address, the message will be delivered from separated MTA.