On the Internal Network
You can deploy ePrism on the Internal Network. Most businesses choose to use this configuration, although it is considered less secure.

ePrism in Parallel with the Firewall
This is the preferred deployment option for ePrism. ePrism's built-in firewall security architecture eliminates the risks associated with deploying an appliance on the perimeter of your network. Deploying the ePrism in parallel with the firewall reduces the overall load on the firewall by eliminating any mail traffic there.

ePrism on the DMZ
Deploying ePrism on the DMZ is an excellent option to be secure. This type of deployment prevents any direct connection from the Internet to the internal servers, but does not ease the existing load on the firewall.

Clustering (with Stateful Failover)
In the event that the primary owner of an email queue is unavailable (e.g. due to system failure), the mirror system can take ownership of the mirrored email queue for delivery.

Without queue replication (stateful failover), a system with undelivered messages may lose email in process if it suddenly fails. In large environments, this could translate into hundreds or thousands of messages lost forever.

Queue replication actively copies any queued email to the mirror system, ensuring that if one system should fail or be taken offline, the mirror system can take ownership of the queued emails and deliver them. If the source system successfully delivers the message, the copy of the message on the mirror server is automatically removed.