User Guide

7-4
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 7 Defining Which Hosts Are Allowed to Connect Using the Host Access Table (HAT)
Defining Remote Hosts into Sender Groups
Sender Group Syntax
Sender Groups Defined by Network Owners, Domains, and IP Addresses
Since the SMTP protocol has no built-in method for authenticating senders of email, senders of
unsolicited bulk email have been successful at employing a number of tactics for hiding their identity.
Examples include spoofing the Envelope Sender address on a message, using a forged HELO address,
Table 7-1 Defining Remote Hosts in the HAT: Sender Group Syntax
Syntax Meaning
n:n:n:n:n:n:n:n
IPv6 address; does not need to include leading zeroes.
n:n:n:n:n:n:n:n-
n:n:n:n:n:n:n:n
n:n:n-n:n:n:n:n:n
Range of IPv6 addresses; does not need to include leading zeroes.
n.n.n.n
Full (complete) IPv4 Address
n.n.n.
n.n.n
n.n.
n.n
n.
n
Partial IPv4 address
n.n.n.n-n
n.n.n-n.
n.n.n-n
n.n-n.
n.n-n
n-n.
n-n
Range of IPv4 addresses
yourhost.example.com
A fully-qualified domain name
.partialhost
Everything within the partialhost domain
n/c
n.n/c
n.n.n/c
n.n.n.n/c
IPv4 CIDR address block
n:n:n:n:n:n:n:n/c IPv6 CIDR address block; does not need to include leading zeroes
SBRS[n:n]
SBRS[none]
SenderBase Reputation Score. For more information, see Defining
Sender Groups by SenderBase Reputation Score, page 7-6.
SBO:n
SenderBase Network Owner Identification Number. For more
information, see Defining Sender Groups by SenderBase
Reputation Score, page 7-6.
dnslist[dnsserver.domain] DNS List query. For more information, see Sender Groups Defined
by Querying DNS Lists, page 7-7.
ALL
Special keyword that matches ALL addresses. This applies only to
the ALL sender group, and is always included (but not listed).