IronPort - advanced configuration guide

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Customizing Listeners
CHAPTER
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In the Cisco IronPort AsyncOS for Email Configuration Guide, you learned how the Cisco IronPort
AsyncOS operating system allows the Cisco IronPort appliance to function as the inbound email gateway
for your enterprise, servicing SMTP connections from the Internet, accepting messages, and relaying
messages to the appropriate systems by enabling listeners to service these connections.
A listener describes an email processing service that will be configured on a particular IP interface.
Listeners only apply to email entering the Cisco IronPort appliance — either from the internal systems
within your network or from the Internet. Cisco IronPort AsyncOS uses listeners to specify criteria that
messages must meet in order to be accepted and relayed to recipient hosts. You can think of a listener as
an “email injector” or even a “SMTP daemon” running on a specific port for each IP address you specify
(including the initial addresses you configured with the System Setup Wizard or systemsetup
command).
Note If you have completed the GUI’s System Setup Wizard (or the Command Line Interface systemsetup
command) as described in the “Setup and Installation” chapter of the Cisco IronPort AsyncOS for Email
Configuration Guide and committed the changes, at least one listener should already be configured on
your appliance.
This chapter describes how to use the Listeners page on the Network menu in the GUI or the
listenerconfig CLI command to customize some of the advanced receiving properties of listeners
configured on your Cisco IronPort appliance, including creating new listeners. The following chapter,
Chapter 2, “Configuring Routing and Delivery Features” describes how to customize the delivery
properties of listeners configured on the system.
The following topics are described:
• Listeners Overview, page 1-2
Configuring Listeners via the GUI, page 1-3
Configuring Listeners via the CLI, page 1-14
SenderBase Settings and HAT Mail Flow Policies, page 1-16
– HAT Significant Bits Feature, page 1-18
Encrypting SMTP Conversations Using TLS, page 1-22
Cisco IronPort AsyncOS 7.6 for Email Advanced Configuration Guide
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