Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

When sending email with bounce verification enabled, your IronPort 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 IronPort 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 IronPort appliance delivering a bounce message to an IronPort 
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 IronPort 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 IronPort Bounce Verification.