Cisco Cisco Email Security Appliance C160 Mode D'Emploi

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Cisco AsyncOS 8.5 for Email User Guide
 
Chapter 9      Using Message Filters to Enforce Email Policies
  Message Filter Rules
The 
$CertificateSigners
 variable expands to:
Examples
The following example inserts a new header if the certificate issuer is from the US:
The following example notifies an administrator if the signer is not from example.com:
The following example adds a header if the message has an X.509 certificate:
The following example adds a header if the message’s certificate does not have a signer:
Header Repeats Rule
The Header Repeats rule evaluates to 
true
 if at a given point in time, a specified number of messages:
With same subject are detected in the last one hour.
From same envelope sender are detected in the last one hour.
You can use this rule to detect high volume emails. For example, political campaigns through certain 
websites may send out emails to organizations in high volumes. Anti-spam engines treat such emails as 
clean, and do not stop the delivery of these emails.
The syntax of this rule is 
header-repeats (<target>, <threshold> [, <direction>])
, where:
"alice@example.com, al@private.example.com, bob@example.com, bob@private.example.com"
Issuer: if signed-certificate("issuer") == "(?i)C=US" {
    insert-header("X-Test", "US issuer");
}
NotOurSigners: if signed-certificate("signer") AND
      signed-certificate("signer") != "example\\.com$" {
    notify("admin@example.com");
}
AnyX509: if signed-certificate ("issuer") {
    insert-header("X-Test", "X.509 present");
}
NoSigner: if not signed-certificate ("signer") {
    insert-header("X-Test", "Old X.509?");
}