+ 0 Votes It appears to seanferd 2 years ago http://www.google.com/search?q=LegacyExchDN + 0 Votes Reponse To Answer jcwfbi 2 years ago Thank you I will check this out. Im trying to understand how many ad attributes control what Exchange does. Answer to your questions: a customer had a Exchange 03 server in co-existence with 2010 and they were unable to see free busy. I was told that this attribute had an effect on 03 seeing free busy from 2010. + 1 Votes LegacyDN dcolbert Contributor Updated - 2 years ago I am familiar with LegacyDN as it relates to a migration from Exchange 5.5 to 2003. I'll relate what I know - the information should help understand how this works in later versions: DN stands for Distinguished Name, and it relates to both Active Directory and Exchange schema keys. In Exchange 5.5, a separate Exchange DN was maintained by the Exchange Server. In Exchange 2003, it became an Active Directory Object. The formats between the two did not remain the same. Microsoft has a utility called LegacyDN that will allow you to view and modify the LegacyDN value. <b>It is not supported for production environments.</b> LegacyDN runs by default in Read Only mode. I will not describe here how to force it into write mode which will allow you to make changes to the legacyExchangeDN stem value. Here is a great article explaining the legacyExchangeDN value: http://www.msexchange.org/tutorials/Understanding-LegacyExchangeDN.html Here is another that seems to relate to this user's question: http://www.microsoftnow.com/2008/07/managing-changes-to-legacyexchangedn.html A Microsoft article: http://technet.microsoft.com/en-us/library/aa997125(EXCHG.80).aspx And finally - a Tech Republic article discussing LegacyExchangeDN http://www.techrepublic.com/article/solutionbase-rename-exchange-active-directory-objects-with-legacyexchangedn/5313400 Those should get you started - they all indicate that the issues you are describing are very likely to be related to the leagacyexchangedn stem value. It is very important that you understand this value completely before making any changes - you can completely hose your Exchange environment and put all of your stores in a state where they will shut down dirty and cannot be brought up without data loss and extensive Exchange DB recovery when messing with this value. It seems like your question needs to supply more information, too: You have Exchange 2010. An Exchange 2003 server was trying to connect to your Exchange 2010 server. Was it an external Exchange 2003 server or one internal to your own environment? The LegacyExchDN value was missing for the user according to the error? What was the result? The mail was undeliverable? Check out page 2 of this document at Umich.edu: http://www.itcs.umich.edu/exchange/docs/undeliverable-messages.pdf It discusses troubleshooting delivery issues with user mail caused by LegacyExchangeDN values that are missing. My guess is that this one should help you, although you'll need to extrapolate the information from the University of Michegan-centric document to your own environment. They recommend: "If this problem does occur, the solution is to modify the users account so that mail can be sent to both accounts. This procedure requires using ADSI Edit, a very powerful and potentially dangerous tool. Before using this procedure, please make sure you know what you are doing. ADSI Edit is part of the Windows 2003 Support Tools which you can download from Microsoft." Good luck!