A most inventive and amusing title to this post, if I do say so myself!
After installing Exchange 2010 into a legacy Exchange 2003 environment, you may be faced with the following error when viewing the properties of an Exchange 2003 mailbox in the Exchange Management Console. In addition to this, if you attempt to migrate a mailbox to Exchange 2010 from 2003, you may see this error:
Mailbox database “EXCHANGE\First Storage Group\Mailbox Store (EXCHANGE)” doesn’t exist.
This is a permissions issue, and the fix is relatively simple:
1. Log into your Exchange 2003 server and open the Exchange System Manager (affectionately known as ESM).
2. Go to the properties of the Mailbox Store mentioned in the error message:
3. Go to the Security Tab of the Mailbox Store and select the Advanced option. Tick the box to ‘Allow inheritable permissions’ , and Apply your changes.
4. If this doesn’t fix your problem, or if the ‘Allow inheritable permissions’ box is already ticked, then do the same thing (Advanced settings under the Security tab, make sure the ‘Allow inheritable permissions’ box is ticked) but to do this, go into the Properties of the server itself, not the Mailbox Store.
5. If even this doesn’t work, then you should manually add in the Exchange 2010 server into the permissions group for the Exchange 2003 server and give it Full Control.
Hope this helps!