I have been working through a migration scenario in a lab environment.  The migration is inter-forest Windows 2003 to Windows 2003 and mailbox migration Exchange Server 2003 SP2 to Exchange Server 2003 SP2.  The ADMT migration of accounts works just fine, but I came across some odd behaviour when running the Exchange Migration Wizard.   Here's the sequence of steps that I used:

• Run ADMT 3.0 to migrate AD accounts with SIDHistory.   Also with option to disable source accounts.
• Run ADModify against disabled source AD accounts to assign SELF the Associated external account permission.  This is to allow the mailbox to be accessed by the Exchange Migration Wizard (EMW).
• See KB 319047 for more information.
• Run EMW selecting option to move mailbox directly to target Exchange server. 
   

At this point I would expect the EMW to find a match between the source and target AD objects (because they were migrated with SIDHistory).  However, this doesn’t happen and instead I get a message saying that there is a naming conflict and EMW prompts me to create an additional account in the target OU. Obviously I don't want to do that.

Knowing that there is a post SP2 hotfix available to change the way in which Exchange handles disabled AD accounts associated with Exchange mailboxes (KB 916783), I installed it.  Here’s the sequence I used after the hotfix install.

• Run ADMT to migrate AD accounts with SIDHistory.   Also with option to disable source accounts.
• Run EMW selecting option to move mailbox directly to target Exchange server.
   

This works fine – in other words EMW matches the source mailbox with the migrated AD account in the target domain.

I’m not sure why my first sequence of steps produced the undesired result, but my guess is  that EMW queries the value of the msExchangeMasterAccountSID (if present), rather than the user object SID.  Because msExchangeMasterAccountSID matches SELF rather than the mailbox’s owning AD object, EMW won’t find a match the migration user object in the target domain.

This behaviour could cause confusion for those migrating who have not yet installed the hotfix.

Tony

Note that if you are running Exchange Server 2003 SP1 you should install a different hotfix (see KB 903158).  If you then subsequently install SP2 you will need to apply the post-SP2 hotfix (see KB 916783).  In other words the post SP1 hotfix didn’t make it into the SP2 build.