Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

The AsyncOS CLI supports more control settings for each SPF/SIDF conformance level. When 
configuring the default settings for a listener’s Host Access Table, you can choose the listener’s 
SPF/SIDF conformance level and the SMTP actions (ACCEPT or REJECT) that the appliance performs, 
based on the SPF/SIDF verification results. You can also define the SMTP response that the appliance 
sends when it rejects a message.

Depending on the conformance level, the appliance performs a check against the HELO identity, MAIL 
FROM identity, or PRA identity. You can specify whether the appliance proceeds with the session 
(ACCEPT) or terminates the session (REJECT) for each of the following SPF/SIDF verification results 
for each identity check:

None. No verification can be performed due to the lack of information.

Neutral. The domain owner does not assert whether the client is authorized to use the given identity.

SoftFail. The domain owner believes the host is not authorized to use the given identity but is not 
willing to make a definitive statement. 

Fail. The client is not authorized to send mail with the given identity. 

TempError. A transient error occurred during verification.

PermError. A permanent error occurred during verification.

The appliance accepts the message for a Pass result unless you configure the SIDF Compatible 
conformance level to downgrade a Pass result of the PRA identity to None if there are Resent-Sender: 
or Resent-From: headers present in the message. The appliance then takes the SMTP action specified for 
when the PRA check returns None.

If you choose not to define the SMTP actions for an identity check, the appliance automatically accepts 
all verification results, including Fail.

The appliance terminates the session if the identity verification result matches a REJECT action for any 
of the enabled identity checks. For example, an administrator configures a listener to accept messages 
based on all HELO identity check results, including Fail, but also configures it to reject messages for a 
Fail result from the MAIL FROM identity check. If a message fails the HELO identity check, the session 
proceeds because the appliance accepts that result. If the message then fails the MAIL FROM identity 
check, the listener terminates the session and then returns the STMP response for the REJECT action.

The SMTP response is a code number and message that the appliance returns when it rejects a message 
based on the SPF/SIDF verification result. The TempError result returns a different SMTP response from 
the other verification results. For TempError, the default response code is 

451

 and the default message 

text is 

#4.4.3 Temporary error occurred during SPF verification

. For all other verification results, 

the default response code is 

550

 and the default message text is 

#5.7.1 SPF unauthorized mail is 

prohibited

. You can specify your own response code and message text for TempError and the other 

verification results. 

Optionally, you can configure the appliance to return a third-party response from the SPF publisher 
domain if the REJECT action is taken for Neutral, SoftFail, or Fail verification result. By default, the 
appliance returns the following response:

    550-#5.7.1 SPF unauthorized mail is prohibited.

    550-The domain example.com explains:

    550 <Response text from SPF domain publisher>