User Guide

9-23
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 9 Using Message Filters to Enforce Email Policies
Message Filter Rules
• Header Repeats Rule, page 9-45
• URL Reputation Rules, page 9-47
• URL Category Rule, page 9-47
• Corrupt Attachment Rule, page 9-47
True Rule
The true rule matches all messages. For example, the following rule changes the IP interface to external
for all messages it tests.
Valid Rule
The valid rule returns false if the message contains unparsable/invalid MIME parts and true otherwise.
For example, the following rule drops all unparsable messages it tests.
Subject Rule
The subject rule selects those messages where the value of the subject header matches the given regular
expression.
For example, the following filter discards all messages with subjects that start with the phrase
Make
Money...
externalFilter:
if (true)
{
alt-src-host('external');
}
not-valid-mime:
if not valid
{
drop();
}
scamFilter:
if (subject == '^Make Money')
{
drop();
}