You have an environment with multiple mail transfer agents (MTAs) that need to send directly to the Network Prevent for Email server.
The RequestProcessor.AllowHosts option lists the hosts that are permitted to send directly to the Prevent server. The field is normally blank (which allows all hosts), but you can enter a maximum of 512 characters. The option is located under System > Servers > Overview, on the configuration page for the Prevent server, then Server Settings.
You cannot add networks using CIDR notation or wildcards, so there is currently no way to combine multiple hosts into a single entry.
In most implementations, the number of hosts sending directly to Prevent should be small, for security and administrative reasons. however, if you need to allow a very large number of hosts to send to Prevent, you can use other means (such as firewall rules, access control lists on network devices, etc.) to accomplish the same goal.
This information applies to legacy version 11.x