Occasionally, I have a domain user that permanently deletes an email they don't intend to. Our Barracuda firewall archives 90 days of inbound messages. When I try to re-deliver one of these messages, the Barracuda successfully hands off to the Exchange 2007 server. However, upon examining activity in the message tracking utility, the server gives the message an eventid of DUPLICATEDELIVER and won't deliver to the mailbox. How do I force delivery of one of these duplicate messages?

http://msexchangeteam.com/archive/2004/07/14/183132.aspx How does duplicate detection work?

This article was written in 2004, but I'll assume the same still applies to Exchange 2007. In any event, the keys that tell the store how long to track duplicates (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<Server Name>\<Private/Public-Guid>\Track Duplicates (in hours)) did not exist, so I added them with the minimum 1 hour value. The keys that control the background cleanup thread (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<Server Name>\<Private/Public-Guid>\Background Cleanup (in msecs)) were set to 60,000 msecs or 1 minute. It had been 18 hours since I last attempted to re-deliver the original message. Re-delivered 10 mins ago and it is still being treated as a duplicate. What am I missing?

Hi, Please refer to the following article to modify relevant settings. http://technet.microsoft.com/en-us/library/dd577073(EXCHG.80).aspx However, it’s not recommended to send duplicate email. You can just save the missing email and copy it to the domain user instead. Thanks.Novak Wu-MSFT