Cisco Cisco Email Security Appliance X1050 Guía Del Usuario
21-53
Cisco AsyncOS 8.0.1 for Email User Guide
Chapter 21 Configuring Routing and Delivery Features
Set Email Delivery Parameters
The Cisco appliance accepts email using multiple mail protocols: SMTP and QMQP. However, all
outgoing email is delivered using SMTP, which is why the
outgoing email is delivered using SMTP, which is why the
deliveryconfig
command does not require
that the protocol be specified.
Note
Several of the features or commands described in this section will affect, or be affected by routing
precedence. Please see Appendix B, “Assigning Network and IP Addresses” in the Cisco IronPort
AsyncOS for Email Configuration Guide for more information.
precedence. Please see Appendix B, “Assigning Network and IP Addresses” in the Cisco IronPort
AsyncOS for Email Configuration Guide for more information.
Default Delivery IP Interface
By default, the system uses an IP interface or IP interface group for email delivery. Any currently
configured IP interface or IP interface group can be set. If no specific interface is identified, AsyncOS
will use the hostname associated with the default delivery interface in the
configured IP interface or IP interface group can be set. If no specific interface is identified, AsyncOS
will use the hostname associated with the default delivery interface in the
SMTP HELO
command when
communicating with recipient hosts. To configure IP interfaces, use the
interfaceconfig
command.
These are the rules for using Auto selection of email delivery interfaces:
•
If the remote email server is on the same subnet as one of the configured interfaces, then traffic will
go out on the matching interface.
go out on the matching interface.
•
When set to auto-select, static routes you have configured using
routeconfig
take effect.
•
Otherwise, the interface that is on the same subnet as the default gateway will be used. If all of the
IP addresses have an equivalent route to the destination, then the system uses the most efficient
interface available.
IP addresses have an equivalent route to the destination, then the system uses the most efficient
interface available.
Possible Delivery Feature
When the Possible Delivery feature is enabled, AsyncOS treats any message that times-out after the body
of the message is delivered, but before recipient host acknowledges receipt of the message, as a “possible
delivery.” This functionality prevents recipients from receiving multiple copies of a message if
continuous errors at their recipient host prevent acknowledgement of receipt. AsyncOS logs this
recipient as a possible delivery in the mail logs and counts the message as completed. It is recommended
that the Possible Delivery feature remains enabled.
of the message is delivered, but before recipient host acknowledges receipt of the message, as a “possible
delivery.” This functionality prevents recipients from receiving multiple copies of a message if
continuous errors at their recipient host prevent acknowledgement of receipt. AsyncOS logs this
recipient as a possible delivery in the mail logs and counts the message as completed. It is recommended
that the Possible Delivery feature remains enabled.
Default Maximum Concurrency
You also specify the default maximum number of concurrent connections the appliance makes for
outbound message delivery. (The system-wide default is 10,000 connections to separate domains.) The
limit is monitored in conjunction with the per-listener maximum outbound message delivery
concurrency (the default per listener is 600 connections for private listeners and 1000 connections for
public listeners). Setting the value lower than the default prevents the Cisco gateway from dominating
weaker networks. For example, certain firewalls do not support large numbers of connections, and the
Cisco could induce Denial of Service (DoS) warnings in these environments.
outbound message delivery. (The system-wide default is 10,000 connections to separate domains.) The
limit is monitored in conjunction with the per-listener maximum outbound message delivery
concurrency (the default per listener is 600 connections for private listeners and 1000 connections for
public listeners). Setting the value lower than the default prevents the Cisco gateway from dominating
weaker networks. For example, certain firewalls do not support large numbers of connections, and the
Cisco could induce Denial of Service (DoS) warnings in these environments.