Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

Submit and commit your changes.

In order to classify connections to the appliance and apply mail flow policies (which may or may not 
contain rate limiting), a listener uses the following methodology: 

Classification -> Sender Group -> Mail Flow Policy -> Rate Limiting 

For more information, see 

. 

The “Classification” stage uses the sending host’s IP address to classify an inbound SMTP session 
(received on a public listener) into a Sender Group. The Mail Flow Policy associated with that Sender 
Group may have parameters for rate limiting enabled. (Rate limiting limits the maximum number of 
messages per session, the maximum number of recipients per message, the maximum message size, 
and/or the maximum number of concurrent connections you are willing to accept from a remote host.)

Normally, in this process, recipients are counted against each sender in the corresponding named sender 
group. If mail is received from several senders in the same hour, the total recipients for all senders is 
compared against the limit.

There are some exceptions to this counting methodology:

If the classification is done by Network Owner, then the SenderBase Reputation Service will 
automatically divide a large block of addresses into smaller blocks. 

Counting of recipients and recipient rate limiting is done separately for each of these smaller blocks 
(usually, but not always, the equivalent of a /24 CIDR block). 

If the HAT Significant Bits feature is used. In this case, a large block of addresses may be divided 
into smaller blocks by applying the significant bits parameter associated with the policy. 

Note that this parameter relates to the Mail Flow Policy -> Rate Limiting phase. It is not the same 
as the “bits” field in the “network/bits” CIDR notation that may be used to classify IP addresses in 
a Sender Group.

By default, SenderBase Reputation Service and IP Profiling support are enabled for public listeners and 
disabled for private listeners. 

When you configure a listener, you can determine how long the appliance caches information queried 
from the SenderBase Reputation Service. Then when you configure a mail flow policy, you can enable 
SenderBase to allow it to control the flow of mail into the listener.

Enable SenderBase in a mail flow policy in the GUI using the “Use SenderBase for Flow Control” setting 
when you configure a mail flow policy, or in the CLI using the 

listenerconfig > hostaccess > edit

 

command.