The mail system-related components and possibly the MDS (Message Distribution Server) are installed behind the firewall, while the kernel performing the system-independent tasks works in front of the firewall on the SIP trunk or PBX. Therefore, there is no direct connection between the external and internal company network at any time.

• Data transport is decoupled and takes place via common transport and safety standards
• Only a few ports with known and manageable protocols must be routed through the firewall
• The data stream can be monitored by the firewall