Cisco Cisco Email Security Appliance C160 Mode D'Emploi

The HAT allows you to specify hosts that are allowed to connect to a listener (that is, which hosts you 
will allow to send email). 

Sender Groups are used to associate one or more senders into groups, upon which you can apply message 
filters, and other Mail Flow Policies. Mail Flow Policies are a way of expressing a group of HAT 
parameters (access rule, followed by rate limit parameters and custom SMTP codes and responses).

Together, sender groups and mail flow policies are defined in a listener’s HAT.

Host DNS verification settings for sender groups allow you to classify unverified senders prior to the 
SMTP conversation and include different types of unverified senders in your various sender groups.

While the connecting host was subject to Host DNS verification in sender groups — prior to the SMTP 
conversation — the domain portion of the envelope sender is DNS verified in mail flow policies, and the 
verification takes place during the SMTP conversation. Messages with malformed envelope senders can 
be ignored. You can add entries to the Sender Verification Exception Table — a list of domains and email 
addresses from which to accept or reject mail despite envelope sender DNS verification settings.

Sender reputation filtering allows you to classify email senders and restrict access to your email 
infrastructure based on sender’s trustworthiness as determined by the Cisco SenderBase Reputation 
Service. 

For more information, see 

.

Using the 

listenerconfig

 command, you can configure a listener to not include the Received: header 

by default to all messages received by the listener.

For more information, see “Advanced Configuration Options” in the “Customizing Listeners” chapter.

You can configure a listener to automatically append a default domain to sender addresses that do not 
contain fully-qualified domain names; these are also known as “bare” addresses (such as “joe” vs. 
“joe@example.com”). 

For more information, see “SMTP Address Parsing Options” in the “Customizing Listeners” chapter.

Outgoing mail is tagged with a special key, and so if that mail is sent back as a bounce, the tag is 
recognized and the mail is delivered. For more information, see “Bounce Verification” in the 
“Configuring Routing and Delivery Features” chapter.