Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

If you enable envelope sender verification or disable allowing partial domains in 
SMTP Address Parsing options for a listener (see the SMTP Address Parsing 
Options section in “Customizing Listeners” in the Cisco IronPort AsyncOS for 
Email Advanced Configuration Guide), the default domain settings for that 
listener will no longer be used.

These features are mutually exclusive.

You can specify the SMTP code and response message for messages with 
malformed envelope senders, for envelope senders which do not exist in DNS, and 
for envelope senders which do not resolve via DNS queries (DNS server might be 
down, etc.). 

In the SMTP response, you can include a variable, 

$EnvelopeSender

, which is 

expanded to the value of the envelope sender when the custom response is sent.

While typically a “Domain does not exist” result is permanent, it is possible for 
this to be a transient condition. To handle such cases, “conservative” users may 
wish to change the error code from the default 5XX to a 4XX code.

The sender verification exception table is a list of domains or email addresses that 
will either be automatically allowed or rejected during the SMTP conversation. 
You can also specify an optional SMTP code and reject response for rejected 
domains. There is only one sender verification exception table per Cisco IronPort 
appliance and it is enabled per mail flow policy.

The sender verification exception table can be used to list obviously fake but 
correctly formatted domains or email addresses from which you want to reject 
mail. For example, the correctly formatted MAIL FROM: 

pres@whitehouse.gov

 

could be listed in the sender verification exception table and set to be 
automatically rejected. You can also list domains that you want to automatically 
allow, such as internal or test domains. This is similar to envelope recipient 
(SMTP RCPT TO command) processing which occurs in the Recipient Access 
Table (RAT).