See Setting the customer-specific spam submission aggressiveness level.
Symantec Messaging Gateway lets you specify who can submit messages for custom rules.
You can specify whether you want all messages that are submitted to be considered for a custom rule.
Or you can specify whether a message must be submitted multiple times from different users before it should be considered.
But first, let's cover some of the fundamental Exchange 2013 concepts that apply here.
Looking at the Exchange 2013 transport architecture there are multiple services involved.
A very common scenario for Exchange Server 2013 administrators is the need to allow applications and devices on the network to use the Exchange server as an SMTP service.
You must have Full Administration, Manage Settings, or Manage Spam Submission modify rights to perform these tasks.
With integrated Live Update functionality, virus definitions can be deployed enterprise-wide without stopping scan services or incurring server downtime.
Basic spam tools include heuristics-based detection, custom filtering rules, and real-time blacklists and whitelisting.
You must enable customer-specific policies for the customer-specific rules to be applied to incoming messages.
See Enabling and disabling spam and unwanted email policies.