Settings in Security.cloud to accept mails from Network Prevent for Email

Hello all,

Trying to setup below mail flow and integrate On premise DLP server with to monitor outbound email traffic from office 365 to symantec security.cloud.

Below is the flow.

Outbound mails from my org -> Office 365 -> Network Prevent for Email (my org's DMZ) -> Office 365 -> Symantec Email Security.cloud -> Internet 

What are the IP addresses that I have to provide in Network Prevent for Email Server to foward the mails to Symantec Security.cloud?

What are the settings I need to do to accept emails from On-Premise Network Prevent for Email server (this server will be on-prem DMZ with a public IP)