Email Recipients not receiving bounce back messages

People who are sending email to a non existent mailbox to our exchange server are not receiving a bounce back message.  It is first filtered through a Barracuda and that indicates the message was delivered to the exchange server.  How do I get messages sent out to the sender if the mailbox don't exist within exchange?
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check the barracuda logs and exchange tracking logs to see where that email is sitting.
Nick RhodeIT DirectorCommented:
I assume its because NDRs (Non Delivery Reports) are turned off on both exchange and the barracuda.  I leave exchange NDRs turned off to prevent backscatter but have it enabled on my external spam filter which is hosted.  I think by default the Barracuda has NDRs turned off and they can be turned on.

Barracuda NDRs

Here is a link on Barracuda's site to explain how you can view the settings of NDRs :)
gprettyAuthor Commented:
The NDRs are on.
Check your exchange log to see if it issues an nor, where is the message sent is it locally delivered, or filtered out through other means.

When the user's send emails, which server do they connect to?  If the client gets an error I.e. 570 no such user, that is their ndr.

The information provided here Is incomplete.
gprettyAuthor Commented:
Thanks for your comments.  Just found that the LDAP was not set on the Barracuda for that particular domain.

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