In Exchange 2003 RUS stamps the LegacyExchangeDN attribute to all mail recipients for purposes of backward compatibility with Exchange 5.5. I'm not sure if its used elsewhere, but it seems this is its only use. In a 2003-2007 environment, objects stamped with RUS get the old administrative group for the LegacyExchangeDN. It would appear this applies to contacts, mailusers and groups. However it seems mailboxes are stamped with the 2007 administrative group. I have confirmed this. The issue is with that .NK2 cache file that Outlook uses for address auto-complete. I have a batch of users I'm converting from mailusers to mailbox users (and vice versa) and as such, their legacy DN is removed then re-stamped with the 2007 administrative group. This results in bad nk2 cache. Purging this cache is overkill, and users depend on this more they should. Any suggestions on how I could make this work better? I assume EAP is stamping mailboxes, while RUS is doing the rest. I'm not ready to remove RUS, so how do I fix this issue in the mean time? (is my overall understanding incorrect - am I missing something?) Ive read other posts as well, but it seems nobody really has found a solid answer.Heres another: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1263565&SiteID=17

Hi, You can take the original legacyexchangedn value and add to the users as a X500 address - this procedure will assure that mail flow will continue without users having to delete their NK2 files. Leif

What is the relationship with x500 addresses and the legacyexchangedn attribute? Also what is x500 used for vs. x400?

Hi, It looks as if the X500 address (= legacyexchangedn) address is used when Outlook caches the names in the NK2 file. So the original legacyexchangedn address is a X500 address. I can't explain it any other way. Leif

First of all, before I get any further, thanks for your time and assistance! Ok, I would agree that the legacyexchangedn is the address cached. Where is it said that this is also called the x500 address? I see x400 in the recipient policy but not x500. It looks like x400 does not include the administrative group in the path, where the legacyexchangedn/x500 does. Anyone have any more detail to what these 3 attributes/addresses are all about? I do know that Exchange 2000/03 MTA uses x400 to route mail, so that explains x400, but what is the purpose for x500, and why is the exchangelegacydn set to use it?

Hi Mike, Please understand when message is submitted through SMTP, the Categorization resolve the sender and recipient based on the proxyAddress attribute in Directory Service. Nevertheless, if the message is submitted via Outlook or OWA, then legacyExchangeDN attribute is used. Therefore, two attributes are checked when message is submitted. If the legacyExchangeDN is modified, you can add X500 Address into proxyAddress according to your NK2 cache. I suggest you read the following blog: Exchange 2007, legacyExchangeDN and mail-enabled user conversions http://mostlyexchange.blogspot.com/2007/08/exchange-2007-legacyexchangedn-and-mail.html Mike

Great - thanks for the links! I guess once we're a native exchange 2007 environment this won't be an issue anymore right? Except for pre-existing cache, of course. I'll add the x500 proxy address as described here: http://support.microsoft.com/kb/313324 & here: http://blog.scottlowe.org/2007/02/15/preserving-nickname-cache-in-exchange-migrations/ Also, I'm still confused about one thing: If I create a mail-user with the exchange 2007 tools, it stamps the legacyexchangedn with the 2003-based administrative group. if i create a user-mailbox it gets the 2007 administrative group? Why is this not consistent? Finally, how do I structure the EAP to apply this? I'm not sure what to use as a variable for the alias.

Ok, I found this: http://blogs.technet.com/mbaher/archive/2008/02/17/auto-complete-reply-ability-i-need-my-x500.aspx -which is a script that applies it, but can this be done with an EAP?