Руководство Пользователя для Cisco Cisco Email Security Appliance C170

Mail Transfer Agent, or Messaging Transfer Agent. The program responsible for 
accepting, routing, and delivering email messages. Upon receiving a message 
from a Mail User Agent or another MTA, the MTA stores a message temporarily 
locally, analyses the recipients, and routes it to another MTA (routing). It may 
edit and/or add to the message headers. The Cisco appliance is an MTA that 
combines hardware, a hardened operating system, application, and supporting 
services to produce a purpose-built, rack-mount server appliance dedicated for 
enterprise messaging.

Mail User Agent. The program that allows the user to compose and read email 
messages. The MUA provides the interface between the user and the Message 
Transfer Agent. Outgoing mail is eventually handed over to an MTA for delivery. 

Specifies the MTA on the Internet responsible for accepting mail for a specified 
domain. A Mail Exchange record creates a mail route for a domain name. A 
domain name can have multiple mail routes, each assigned a priority number. 
The mail route with the lowest number identifies the primary server responsible 
for the domain. Other mail servers listed will be used as backup.

A bounce that occurs due to a message being returned after the message was 
accepted for delivery by the recipient host. These can be soft (4XX) or hard 
(5XX) bounces. You can analyze these bounce responses to determine what to 
do with the recipient messages (e.g. re-send soft bounced recipient messages and 
remove hard bounced recipients from database).

Network Time Protocol. The 

ntpconfig

 command configures IronPort 

AsyncOS to use Network Time Protocol (NTP) to synchronize the system clock 
with other computers.

An open relay (sometimes called an “insecure relay” or a “third party” relay) is 
an SMTP email server that allows unchecked third-party relay of email 
messages. By processing email that is neither for nor from a local user, an open 
relay makes it possible for an unknown senders to route large volumes of email 
(typically spam) through your gateway. The 

listenerconfig

 and 

systemsetup

 commands prevent you from unintentionally configuring your 

system as an open relay.

IronPort’s Outbreak Filters feature provides an additional layer of protection 
from viruses. The Outbreak Filters feature quarantines suspicious email 
messages, holding the messages until an updated virus IDE is available. or until 
they are deemed not a threat.