IronPort - advanced configuration guide

Handling Undeliverable Email
Notes on Soft and Hard Bounces
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Cisco IronPort AsyncOS 7.6 for Email Advanced Configuration Guide
Chapter 2 Configuring Routing and Delivery Features
The Cisco IronPort AsyncOS operating system classifies undeliverable email, or “bounced messages,”
into the following categories:
“Conversational” bounces:
The remote domain bounces the message during the initial SMTP conversation.
Soft bounces A message that is temporarily undeliverable. For example, a user’s mailbox may be
full. These messages can be retried at a later time. (e.g. An SMTP 4XX error code.)
Hard bounces A message that is permanently undeliverable. For example, the user no longer exists
for that domain. These messages will not be retried. (e.g. An SMTP 5XX error code.)
“Delayed” (or “Non-conversational”) bounces:
The remote domain accepts the message for delivery, only to bounce it at a later time.
Soft bounces A message that is temporarily undeliverable. For example, a user’s mailbox may be
full. These messages can be retried at a later time. (e.g. An SMTP 4XX error code.)
Hard bounces A message that is permanently undeliverable. For example, the user no longer exists
for that domain. These messages will not be retried. (e.g. An SMTP 5XX error code.)
You use the Bounce Profiles page on the Network menu in the GUI (or the bounceconfig command) to
configure how Cisco IronPort AsyncOS handles hard and soft conversational bounces for each listener
you create. You create bounce profiles and then apply profiles to each listener via the Network >
Listeners page (or the listenerconfig command). You can also assign bounce profiles to specific
messages using message filters. (See Chapter 6, “Using Message Filters to Enforce Email Policies” for
more information.)
For conversational soft bounces, a soft bounce event is defined as each time a recipient delivery
temporarily fails. A single recipient may incur several soft bounce events. You use the Bounce
Profiles page or the bounceconfig command to configure parameters for each soft bounce event.
(See Bounce Profile Parameters, page 2-37.)
By default, the system generates a bounce message and sends it to the original sender for each hard
bounced recipient. (The message is sent to the address defined in the Envelope Sender address of
the message envelope. Envelope From is also commonly referred to as the Envelope Sender.) You
can disable this feature and instead rely on log files for information about hard bounces. (See
“Logging” in the Cisco IronPort AsyncOS for Email Daily Management Guide.)
Soft bounces become hard bounces after the maximum time in queue or the maximum number of
retries, whichever comes first.
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