If a Smart Host is not configured, Trellix DLP Network Prevent appliance can't accept email messages because it has nowhere to send them to.
Trellix DLP Network Preventissues a 451 System problem: retry later. (No SmartHost has been configured) error, and closes the connection.
Tip
You can check whether Trellix DLP Network Prevent can accept email using telnet. If the appliance is correctly configured, you get a 220 welcome message:
220 host.domain.example PVA/SMTP Ready
To resolve a connection issue, you must:
Install the necessary extensions in ePO - On-prem.
Register the appliance with a ePO - On-prem.
Follow the steps in the Setup Wizard help.
Configure at least one DNS server in the Common Appliance Management policy.
Configure a Smart Host in the Trellix DLP Network Prevent Email Settings policy category.
Apply a Trellix Data Loss Prevention policy.
See the policy assignment section in the Trellix ePolicy Orchestrator - On-premises Product Guide.