Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

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, or simply 
rotating through different domain names. This leaves many mail administrators 
asking themselves the fundamental question, “Who is sending me all of this 
email?” To answer this question, the SenderBase Reputation Service has 
developed a unique hierarchy for aggregating identity-based information based on 
the IP address of the connecting host — the one thing that is almost impossible 
for a sender to forge in a message.

An IP Address is defined as the IP address of the sending mail host.

A Domain is defined as an entity that uses hostnames with a given second-level 
domain name (for example, yahoo.com), as determined by a reverse (PTR) lookup 
on the IP address. 

A Network Owner is defined as an entity (usually a company) that controls a 
block of IP addresses, as determined based on IP address space assignments from 
global registries such as ARIN (the American Registry for Internet Numbers) and 
other sources.

An Organization is defined as an entity that most closely controls a particular 
group of mail gateways within a network owner’s IP block, as determined by 
SenderBase. An Organization may be the same as the Network Owner, a division 
within that Network Owner, or a customer of that Network Owner.

dnslist[dnsserver.domain] DNS List query. For more information, see 

ALL

Special keyword that matches ALL addresses. This 
applies only to the ALL sender group, and is always 
included (but not listed).