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Bruce HorstmanshofFlag for United States of America

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Resending email problem

I have an Exchange 2010 server running on a Server 2008.  I just found out that users are resending emails, and while their sent items show the email was sent, the recipient never gets the email.
In testing, I sent, then resent myself an email to my personal email and both cam through.
I attempted the same test to an internal address (ie an address on the Exchange server) and I only get the first email.
I deleted the original and tried the re-send operation again and the email was delivered.

Is this behaviour by design, or do I have a problem that I need to address?
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what do you mean by 're-sending' an email?  Are you talking about forwarding an email or composing another email with identical content or what?
No, this is not by design - if you send an email internally it has to get delivered OR you get an NDR, there is no second way out.

If the email isn't getting delivered in first place, track the message using the following cmdlet on hub server

Get-MessageTrackinglog -sender "Sender Email Address" -Recipients "Recipient Email Address" -MessageSubject "Subject line of the test email" -Server "HubServerName" | FL

Once done, provide the details of what you see in the Exchange shell

I am assuming that when you say re-send you mean like this

As exchange-geek has said "No this is not by design" Just tested it on my system and it delivers the second one as it should. Yes this was all internal to the exchange server.

i would be looking at your logs as above to see what is happening.

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Yeah, Funny how no matter how long you have been using something someone always finds something that you never new existed ;)

Really need to see the tracking log to know whats happening to the message.

Shouldnt be a duplicate deliver problem as new message should have new id.

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Thanks to all for the responses.  
It appears that the issue is by design after all, as per the thread provided by marcustech.  This describes exactly what I am getting. The problem being that Exchange tracks the message ID and will not deliver the if it exists.  Using the Outlook resend feature apparently maintains the message ID and so, is considered a duplicate, even if the email has been changed.
I stumbled on a link to indicating that the Duplicate message detection function can be disabled by going to:
and adding a new DWORD value "Disable All Duplicate Detection" and setting the value to 1.
However, this did not work for me.  Are there any suggestions along those lines?
That's odd Podman, as I started trying to test this theory and I felt that my results did not fit with the issue you described.  Have you been able to confirm that the second message gets assigned the same messageID by outlook?

I'll try and test again.
it is odd, and when testing on my exchange 2010 system i could not replicate the result.
Everything i have read on the issue is that it depends on roll-ups etc... and that the method KB975990 that you have used, whilst being for 2007, still applies for 2010.

Have you re-booted the server after making the changes?

I have tested, and the re-sent message is given a rejection as a duplicate code (there was a test which eludes me at this time - but the log showed the rejection condition).
I did restart the server over the weekend (which is why I took so long to post back).  I also verified that I have the correct key added (spelleing, location, etc).
Further testing shows that if I wait one hour and resend the email, it is delivered.
I see a "Track Duplicates" value under HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/MSExchangeIS/ParametersPrivate
which is set to "1".  I am wondering if that needs to be set to "0".

Marcustech - could you see what value you working server has?
On my 'vanilla' SBS 2011 install I have that key with value 1.  I haven't got a handy outlook set up to test on this box with though.  Give me a day or two and I may find time to test properly.  Looks like you might be there though, I'd try setting it to 0 and restarting the service.
Actually, this technet article for Exchange 2007 suggests adding a registry entry 'DeliveredTo Expiration in Hours'  but also cautions "The minimum value that you can set for the DeliveredTo Expiration in Hours registry value is 1 hour. Therefore, Duplicate Message Detection cannot be turned off in Microsoft Exchange. "

Good old MS documentation :)
FWIW i just had a look on my Exchange 2010 environment that i can succesfully resend an email (within 30 seconds ), and my key for Track duplicates as above is set to 1

Tracking log shows same MessageID and that its delivered.

Andrew - are you sending outside the organization?  I can resend to my personal email succesfully, but I have to wait the hour to resend to a user inside the organization.
No all internal to the organization (from to ). Client is outlook 2010, if that makes a difference (it shouldnt).

So... for what it is worth, I set the TrackDuplicates key to 0, and restarted the server last night and I am stil unable to re-send an email within the hour.  
I will have to accept that what ever difference in patching or version I have, it is not possible to resend and it is by design.
Thank you all for you input.
yes, unfortuantly i think that is the case.