We are in the process of beginning to migrate from Exchange 2003 to 2010. We are finding that quite a few permissions on the 2003 mailbox are not being transferred when the mailbox is moved to 2010.
When viewing the permissions of a mailbox under "Mailbox Rights" in 2003 we can see users or groups with various permissions, some set explicitly, some inherited.
I believe (but can't be 100% sure as we have only moved a few mailboxes so far) that the permissions which are missing are the ones inherited from either the mail store or server level (or above) on the Exchange 2003 side.
I realise that some things are different on the 2010 system (i.e. no storage groups etc) so there may not be an equivalent "level" compared to 2003. But is there any way to ensure the permissions are kept without checking 3000 users individually ?