IMSS policies are rules that are applied to SMTP and POP3 messages. Create rules to enforce your organization’s antivirus and other security goals. By default, IMSS includes a Global Antivirus rule to help protect your network from viruses and related Internet threats. Because an antivirus rule addresses the most critical and potentially damaging types of messages, you should always keep it in the first position on the rule list so IMSS can analyze traffic for virus content first.

The antivirus rule does not protect against spam. For the best protection against spam, configure a custom rule that includes spam in the scanning conditions, and activate the IP Filtering product.