Cisco Cisco Email Security Appliance C670 用户指南
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User Guide for AsyncOS 10.0 for Cisco Email Security Appliances
Chapter 26 Configuring Routing and Delivery Features
Directing Bounced Email
the maximum retry interval of 60 seconds. Thus, the second retry attempt is made at approximately
t=120. Immediately after this retry attempt, the system generates a hard bounce message for that
recipient because the maximum number of retries is two.
t=120. Immediately after this retry attempt, the system generates a hard bounce message for that
recipient because the maximum number of retries is two.
In Example 2, the first delivery attempt is made at t=0 and the first retry is made at t=60. The system
hard bounces the message immediately before the next delivery attempt (scheduled to occur at t=120)
because it has exceeded the maximum time in queue of 100 seconds.
hard bounces the message immediately before the next delivery attempt (scheduled to occur at t=120)
because it has exceeded the maximum time in queue of 100 seconds.
Delivery Status Notification Format
Bounce messages generated by the system, by default, use the Delivery Status Notification (DSN) format
for both hard and soft bounces. DSN is a format defined by RFC 1894 (see
for both hard and soft bounces. DSN is a format defined by RFC 1894 (see
http://www.faqs.org/rfcs/rfc1894.html
) that “defines a MIME content-type that may be used by a
message transfer agent (MTA) or electronic mail gateway to report the result of an attempt to deliver a
message to one or more recipients.” By default, the delivery status notification includes an explanation
of the delivery status and the original message if the message size is less than 10k. If the message size
is greater than 10k, the delivery status notification includes the message headers only. If the message
headers exceed 10k, the delivery status notification truncates the headers. If you want include messages
(or message headers) that are greater than 10k in the DSN, you can use the
message to one or more recipients.” By default, the delivery status notification includes an explanation
of the delivery status and the original message if the message size is less than 10k. If the message size
is greater than 10k, the delivery status notification includes the message headers only. If the message
headers exceed 10k, the delivery status notification truncates the headers. If you want include messages
(or message headers) that are greater than 10k in the DSN, you can use the
max_bounce_copy
parameter
in the
bounceconfig
command (this parameter is only available from the CLI).
Delay Warning Messages
Time in Queue Messages (delay notification messages) generated by the system also use the DSN
format. Change the default parameters by using the Bounce Profiles page on the Network menu (or the
format. Change the default parameters by using the Bounce Profiles page on the Network menu (or the
bounceconfig
command) to edit existing or create new bounce profiles and change the default values
for:
•
The minimum interval between sending delay warning messages.
•
The maximum number of delay warning messages to send per recipient.
Delay Warning Messages and Hard Bounces
Note that it is possible to receive both a delay warning and a hard bounce for the same message
simultaneously, if you have set a very small durations for both the “Maximum Time in Queue” setting
and the minimum interval setting for “Send Delay Warning Messages.” Cisco Systems recommends
using the default values for these settings as a minimum if you choose to enable sending of delay warning
messages.
simultaneously, if you have set a very small durations for both the “Maximum Time in Queue” setting
and the minimum interval setting for “Send Delay Warning Messages.” Cisco Systems recommends
using the default values for these settings as a minimum if you choose to enable sending of delay warning
messages.
Further, delay warning messages and bounce messages originated by the appliance may be delayed by
as much as 15 minutes during processing.
as much as 15 minutes during processing.
Table 26-7
Example 2: Bounce Profile Parameters
Parameter
Value
Max number of retries
100
Max number of seconds in queue
100 seconds
Initial number of seconds before retrying
60 seconds
Max number of seconds to wait before retrying
120 seconds