Introduction
This document describes the differences between the "inital... wait" and "maximum... wait" configuration values in the bounce configuration on the Cisco Email Security Appliance (ESA).
What is the relationship between "initial... wait" and "maximum... wait" values in bounceconfig?
In the configuration options for bounceconfig, the "initial number of seconds to wait before retrying a message" is the time to wait after the first unsuccessful attempt to deliver mail for a responsive mail server.
Please enter the initial number of seconds to wait before
retrying a message.
[60]>
Note: By default, the ESA sets this value to 60 seconds.
Note: Unsuccessful attempts are 4xx SMTP response codes. Please see Simple Mail Transfer Protocol (SMTP) Enhanced Status Codes Registry .
The "maximum number of seconds to wait before retrying a message" is recommended according to RFC 2821, section 4.5.4 Retry Strategies - to be greater than 1800 seconds.
Please enter the maximum number of seconds to wait before retrying a message.
[3600]>
Note: By default, the ESA sets this value to 3600 seconds or 1 hour.
As for why it is the 'maximum' value, and not just a retry interval, as also mentioned in the same RFC 2821, section 4.5.4 Retry Strategies, "The sender MUST delay retrying a particular destination after one attempt has failed. In general, the retry interval SHOULD be at least 30 minutes; however, more sophisticated and variable strategies will be beneficial when the SMTP client can determine the reason for non-delivery."
Therefore, if a new mail to a domain is successful, all mails that were previously queued and had retry intervals will be re-attempted for delivery immediately.
Both values should not be confused with the "initial..wait" and "maximum...wait" values for unreachable hosts which serve a similar purpose but are intervals associated with network transport and/or service availability issues as opposed to mail server errors.
Please enter the initial number of seconds to wait before retrying a host that is
unreachable.
[60]>
Please enter the maximum number of seconds to wait before retrying a host that is
unreachable.
[3600]>
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