Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

(Optional) Configure advanced settings for customizing the behavior of the listener as defined in the 
following table. 

(Optional) Configure settings for controlling LDAP queries associated with this listener as defined in the 
following table.

Use these settings to enable LDAP queries on the listener. You must create the LDAP query first, before 
using this option. Each type of query has a separate subsection to configure. Click the type of query to 
expand the subsection.

Maximum Concurrent 
Connections

The maximum number of connections allowed.

TCP Listen Queue Size

The backlog of connections that AsyncOS will manage before the SMTP 
server accepts them.

CR and LF Handling

Choose how to handle messages that contain bare CR (carriage return) and 
LF (line feed) characters. 

Clean. Allows the message, but converts bare CR and LF characters to 
CRLF characters.

Reject. Rejects the message.

Allow. Allows the message.

Add Received Header

Add a received header to all received email. A listener also modifies email 
that it relays by adding a Received: header on each message. If you do not 
want to include the Received: header, you can disable it using this option.

The Received: header is not added to the message within the work 
queue processing. Rather, it is added when the message is enqueued 
for delivery.

Disabling the received header is a way to ensure that your network’s 
topology is not exposed by revealing the IP addresses or hostnames of 
internal servers on any messages traveling outside your infrastructure. 
Please use caution when disabling the received header.

Use SenderBase IP 
Profiling

Choose whether or not to enable SenderBase IP Profiling and configure the 
following settings:

Timeout for Queries. Define how long the appliance caches 
information queried from the SenderBase Reputation Service.

SenderBase Timeout per Connection. Define how long the appliance 
caches SenderBase information per SMTP connection.