Руководство Пользователя для Cisco Cisco Email Security Appliance C170
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Cisco AsyncOS 8.0.2 for Email User Guide
Chapter 21 Configuring Routing and Delivery Features
Configuring Mail Gateways for all Hosted Domains Using Virtual Gateway™ Technology
The Cisco Virtual Gateway technology allows you to configure enterprise mail gateways for all domains
you host — with distinct IP addresses, hostname and domains — and create separate corporate email
policy enforcement and anti-spam strategies for those domains, while hosted within the same physical
appliance.
you host — with distinct IP addresses, hostname and domains — and create separate corporate email
policy enforcement and anti-spam strategies for those domains, while hosted within the same physical
appliance.
Note
The number of Virtual Gateway addresses available to you depends on the model of your Cisco
appliance. Some appliance models can be upgraded to support more Virtual Gateway addressed via a
feature key. Contact your Cisco sales representative for more information about upgrading the number
of Virtual Gateway addresses on your appliance.
appliance. Some appliance models can be upgraded to support more Virtual Gateway addressed via a
feature key. Contact your Cisco sales representative for more information about upgrading the number
of Virtual Gateway addresses on your appliance.
Overview
Cisco has developed a unique Virtual Gateway technology designed to help ensure that corporations can
reliably communicate with their customers via email. Virtual Gateway technology enables users to
separate the Cisco appliance into multiple Virtual Gateway addresses from which to send and receive
email. Each Virtual Gateway address is given a distinct IP address, hostname and domain, and email
queue.
reliably communicate with their customers via email. Virtual Gateway technology enables users to
separate the Cisco appliance into multiple Virtual Gateway addresses from which to send and receive
email. Each Virtual Gateway address is given a distinct IP address, hostname and domain, and email
queue.
Assigning a distinct IP address and hostname to each Virtual Gateway address ensures that email
delivered through the gateway will be properly identified by the recipient host and prevents critical email
from being blocked as spam. The Cisco appliance has the intelligence to give the correct hostname in
the
delivered through the gateway will be properly identified by the recipient host and prevents critical email
from being blocked as spam. The Cisco appliance has the intelligence to give the correct hostname in
the
SMTP HELO
command for each of the Virtual Gateway addresses. This ensures that if a receiving
Internet Service Provider (ISP) performs a reverse DNS look-up, the Cisco appliance will match the IP
address of the email sent through that Virtual Gateway address. This feature is extremely valuable,
because many ISPs use a reverse DNS lookup to detect unsolicited email. If the IP address in the reverse
DNS look-up does not match the IP address of the sending host, the ISP may assume the sender is
illegitimate and will frequently discard the email. The Cisco Virtual Gateway technology ensures that
reverse DNS look-ups will always match the sending IP address, preventing messages from being
blocked accidentally.
address of the email sent through that Virtual Gateway address. This feature is extremely valuable,
because many ISPs use a reverse DNS lookup to detect unsolicited email. If the IP address in the reverse
DNS look-up does not match the IP address of the sending host, the ISP may assume the sender is
illegitimate and will frequently discard the email. The Cisco Virtual Gateway technology ensures that
reverse DNS look-ups will always match the sending IP address, preventing messages from being
blocked accidentally.
Messages in each Virtual Gateway address are also assigned to a separate message queue. If a certain
recipient host is blocking email from one Virtual Gateway address, messages intended for that host will
remain in the queue and eventually timeout. But messages intended for the same domain in a different
Virtual Gateway queue that is not being blocked will be delivered normally. While these queues are
treated separately for delivery purposes, the system administration, logging and reporting capability still
provide a holistic view into all Virtual Gateway queues as if they were one.
recipient host is blocking email from one Virtual Gateway address, messages intended for that host will
remain in the queue and eventually timeout. But messages intended for the same domain in a different
Virtual Gateway queue that is not being blocked will be delivered normally. While these queues are
treated separately for delivery purposes, the system administration, logging and reporting capability still
provide a holistic view into all Virtual Gateway queues as if they were one.
Setting Up Virtual Gateway Addresses
Before setting up the Cisco Virtual Gateway addresses, you must allocate a set of IP addresses that will
be used to send email from. (For more information, see “Assigning Network and IP Addresses” in the
Cisco IronPort AsyncOS for Email Configuration Guide.) You should also ensure proper configuration
of your DNS servers so that the IP address resolves to a valid hostname. Proper configuration of DNS
servers ensures that if the recipient host performs a reverse DNS lookup, it will resolve to valid
IP/hostname pairs.
be used to send email from. (For more information, see “Assigning Network and IP Addresses” in the
Cisco IronPort AsyncOS for Email Configuration Guide.) You should also ensure proper configuration
of your DNS servers so that the IP address resolves to a valid hostname. Proper configuration of DNS
servers ensures that if the recipient host performs a reverse DNS lookup, it will resolve to valid
IP/hostname pairs.