Exchange 2013 Shadow redundancy and Transport dumpster

In Exchange 2013
If I understand when an email is sent from one user to another , a copy of the email is kept somewhere (transport Dumpster), until the destination server(it could be the same where the sender mailbox is), will acknowledge the successful receipt of the message, and the dumpster keeping- time  expires , then the email will be deleted from the dumpster.

I wonder if shadow redundancy is just a different word but the same thing as Transport dumpster.

any idea?

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Ganesh Kumar ASr Infrastructure SpecialistCommented:
I think you are referring it to mail Queue Database on Transport Servers. Actually the queue database stores the information processed, to be processed, and bad mail queue. It gets stored in the transport server. Please read :
Manikandan NarayanswamySecurity Specialist & IBM Security GuardiumCommented:

The Shadow Redundancy is a Function where the emails which are sent are kept until the next hop server confirms its delivery in-case if the email is lost due to server unavailability the entire email sets can be recovered from Shadow redundancy. In exchange 2010 this function is there with the Hub Transport Server. However with Exchange 2013 since there is HT role this is taken care by services.

jskfanAuthor Commented:
What I am trying to understand is the difference between :
Shadow redundancy and Transport dumpster. Do they mean the same thing ?
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Manikandan NarayanswamySecurity Specialist & IBM Security GuardiumCommented:

Transport dumpster is a feature built into Exchange Server 2010 HUB transport role and designed to minimize data loss during mail delivery to a DAG in a lossy failover scenario. The transport dumpster is stored inside the mail.que file. It's only available for message delivery in a cluster continuous replication (CCR) environment and doesn't address potential message loss when messages are in transit between Hub Transport and Edge Transport servers.
With shadow redundancy, the deletion of a message from the transport databases is delayed until the transport server verifies that all of the next hops for that message have completed delivery. If any of the next hops fail before reporting back successful delivery, the message is resubmitted for delivery to that next hop.

For more information refer the below links please

Understanding Shadow redundancy

jskfanAuthor Commented:

I looked up already  that article online.
There are Shadow redundancy term, as well as Transport dumpster which is also called safety Net.
Now we are in Exchange 2013...forget about previous version. which term is used ?
Manikandan NarayanswamySecurity Specialist & IBM Security GuardiumCommented:

In Exchange 2013 Shadow Redundancy supports both it supports DAG & Active-Directory Site available boundaries and the Tranport dumpster is known as Safely Net which stores messages which are processed by the Transport Service in Exchange 2013

For more information in depth refer the below link


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jskfanAuthor Commented:
I have read about Safety Net and Shadow redundancy. I understood they mean the same thing.

in the nutshell Safety Net means:
When a mailbox server 1 receives a message, it notifies mailbox server 2  to create a copy of the message.
Then mailbox server 1 will proceed in delivering the message the right mailbox,
then MB server 1  notifies mailbox server 2 that the message was delivered successfully
MB server 2 will delete the message from the queue after the hold down time expires

Shadow redundancy is the same thing if I am not wrong.

Correct ?

Unless if Shadow redundancy is a term used in Exchange versions prior to 2013 and Safety Net is used in 2013
jskfanAuthor Commented:
Thank you
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