User Guide

CHAPTER
7-1
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
7
Defining Which Hosts Are Allowed to Connect
Using the Host Access Table (HAT)
• Overview of Defining Which Hosts Are Allowed to Connect, page 7-1
• Defining Remote Hosts into Sender Groups, page 7-3
• Defining Access Rules for Email Senders Using Mail Flow Policies, page 7-8
• Understanding Predefined Sender Groups and Mail Flow Policies, page 7-11
• Handling Messages from a Group of Senders in the Same Manner, page 7-13
• Working with the Host Access Table Configuration, page 7-21
• Using a List of Sender Addresses for Incoming Connection Rules, page 7-22
• SenderBase Settings and Mail Flow Policies, page 7-23
• Verifying Senders, page 7-28
Overview of Defining Which Hosts Are Allowed to Connect
For every configured listener, you must define a set of rules that control incoming connections from
remote hosts. For example, you can define remote hosts and whether or not they can connect to the
listener. AsyncOS allows you to define which hosts are allowed to connect to the listener using the Host
Access Table (HAT).
The HAT maintains a set of rules that control incoming connections from remote hosts for a listener.
Every configured listener has its own HAT. You configure HATs for both public and private listeners.
To control incoming connections from remote hosts, you define the following information:
• Remote hosts. Define the way in which a remote host attempts to connect to the listener. You group
remote host definitions into sender groups. For example, you can define multiple remote hosts in a
sender group by IP address and partial hostname. You can also define remote hosts by their
SenderBase reputation score. For more information, see Defining Remote Hosts into Sender Groups,
page 7-3.
• Access rules. You can define whether the defined remote hosts in the sender group are allowed to
connect to the listener and under what conditions. You define access rules using mail flow policies.
For example, you can define that a particular sender group is allowed to connect to the listener, but
only allow a maximum number of messages per connection. For more information, see Defining
Access Rules for Email Senders Using Mail Flow Policies, page 7-8