Cisco Cisco Email Security Appliance C160 Mode D'Emploi

For inbound email only, the RAT allows you to specify a list of all local domains for which the Cisco 
appliance will accept mail.

For more information, see 

Alias tables provide a mechanism to redirect messages to one or more recipients. Aliases are stored in a 
mapping table. When the envelope recipient (also known as the Envelope To, or 

RCPT TO

) of an email 

matches an alias as defined in an alias table, the envelope recipient address of the email will be rewritten. 

For more information about Alias Tables, see “Creating Alias Tables” in the “Configuring Routing and 
Delivery Features” chapter of the Cisco IronPort AsyncOS for Email Advanced Configuration Guide.

You can use your existing LDAP infrastructure to define how the recipient email address of incoming 
messages (on a public listener) should be handled during the SMTP conversation or within the 
workqueue. See “Accept Queries” in the “Customizing Listeners” chapter of the Cisco IronPort AsyncOS 
for Email Advanced Configuration Guide. This allows the Cisco appliance to combat directory harvest 
attacks (DHAP) in a unique way: the system accepts the message and performs the LDAP acceptance 
validation within the SMTP conversation or the work queue. If the recipient is not found in the LDAP 
directory, you can configure the system to perform a delayed bounce or drop the message entirely.

For more information, see the “LDAP Queries” chapter in the Cisco IronPort AsyncOS for Email 
Advanced Configuration Guide.

When you configure your Email Security appliance for SMTP call-ahead recipient validation, the Email 
Security appliance suspends the SMTP conversation with the sending MTA while it “calls ahead” to the 
SMTP server to verify the recipient. When the Cisco appliance queries the SMTP server, it returns the 
SMTP server’s response to the Email Security appliance. The Email Security appliance resumes the 
SMTP conversation and sends a response to the sending MTA, allowing the conversation to continue or 
dropping the connection based on the SMTP server response (and settings you configure in the SMTP 
Call-Ahead profile).

For more information, see the “Validating Recipients Using an SMTP Server” chapter in the Cisco 
IronPort AsyncOS for Email Advanced Configuration Guide.

The Work Queue is where the received message is processed before moving to the delivery phase. 
Processing includes masquerading, routing, filtering, safelist/blocklist scanning, anti-spam and 
anti-virus scanning, Outbreak Filters, and quarantining.