Cisco Cisco Email Security Appliance C160 Mode D'Emploi

Use the Import Table button on the Destination Controls page or the 

destconfig 

-> import

 command to import a configuration file.You can also export your 

Destination Control entries to an INI file using the Export Table button on the 
Destination Controls page or the 

destconfig -> export

 command. AsyncOS 

includes the 

[Default]

 domain control entry in the exported INI file.

You can use the 

destconfig

 command in the CLI to configure Destination 

Control entries. This command is discussed in the Cisco IronPort AsyncOS CLI 
Reference Guide.

A “bounce” message is a new message that is sent by a receiving MTA, using the 
Envelope Sender of the original email as the new Envelope Recipient. This bounce 
is sent back to the Envelope Recipient (usually) with a blank Envelope Sender 
(MAIL FROM: < >) when the original message is undeliverable (typically due to 
a non-existent recipient address).

Increasingly, spammers are attacking email infrastructure via misdirected bounce 
attacks. These attacks consist of a flood of bounce messages, sent by unknowing, 
legitimate mail servers. Basically, the process spammers use is to send email via 
open relays and “zombie” networks to multiple, potentially invalid addresses 
(Envelope Recipients) at various domains. In these messages, the Envelope 
Sender is forged so that the spam appears to be coming from a legitimate domain 
(this is known as a “Joe job”). 

In turn, for each incoming email with an invalid Envelope Recipient, the receiving 
mail servers generate a new email — a bounce message — and send it along to 
the Envelope Sender at the innocent domain (the one whose Envelope Sender 
address was forged). As a result, this target domain receives a flood of 
“misdirected” bounces — potentially millions of messages. This type of 
distributed denial of service attack can bring down email infrastructure and render 
it impossible for the target to send or receive legitimate email.

To combat these misdirected bounce attacks, AsyncOS includes IronPort Bounce 
Verification. When enabled, IronPort Bounce Verification tags the Envelope 
Sender address for messages sent via your IronPort appliance. The Envelope 
Recipient for any bounce message received by the IronPort appliance is then