Cisco Cisco Email Security Appliance C160 Mode D'Emploi

Note that you can use Bounce Verification to manage incoming bounce messages based on your outgoing 
mail. To control how your appliance generates outgoing bounces (based on incoming mail), see 

.

When sending email with bounce verification enabled, your appliance will rewrite the Envelope Sender 
address in the message. For example, MAIL FROM: 

joe@example.com

 becomes MAIL FROM: 

prvs=joe=123ABCDEFG@example.com

. The 

123...

 string in the example is the “bounce verification tag” 

that gets added to the Envelope Sender as it is sent by your appliance. The tag is generated using a key 
defined in the Bounce Verification settings (see 

 

for more information about specifying a key). If this message bounces, the Envelope Recipient address 
in the bounce will typically include this bounce verification tag.

You can enable or disable bounce verification tagging system-wide as a default. You can also enable or 
disable bounce verification tagging for specific domains. In most situations, you would enable it by 
default, and then list specific domains to exclude in the Destination Controls table (see 

).

If a message already contains a tagged address, AsyncOS does not add another tag (in the case of an 
appliance delivering a bounce message to an appliance inside the DMZ).

Bounces that include a valid tag are delivered. The tag is removed and the Envelope Recipient is restored. 
This occurs immediately after the Domain Map step in the email pipeline. You can define how your 
appliances handle untagged or invalidly tagged bounces — reject them or add a custom header. See 

 for more information.

If the bounce verification tag is not present, or if the key used to generate the tag has changed, or if the 
message is more than seven days old, the message is treated as per the settings defined for Bounce 
Verification. 

For example, the following mail log shows a bounced message rejected by the appliance:

Fri Jul 21 16:02:19 2006 Info: Start MID 26603 ICID 125192

Fri Jul 21 16:02:19 2006 Info: MID 26603 ICID 125192 From: <>

Fri Jul 21 16:02:40 2006 Info: MID 26603 ICID 125192 invalid bounce, rcpt address 

<bob@example.com> rejected by bounce verification.

Fri Jul 21 16:03:51 2006 Info: Message aborted MID 26603 Receiving aborted by sender

Fri Jul 21 16:03:51 2006 Info: Message finished MID 26603 aborted