The resolution has been provided by support (although it did take them 4 days to call back!!!! - I logged the call as critical).
Description of problem
======================
We now check to see if the system mailbox exists by trying to create a new one – requires permissions to create users in AD!!
In V5, if you told EV to create the system mailbox for an Archiving Service then, on top of having full administrator rights
on the Exchange Server, the VSA needed to have Create User object privs in AD. To avoid this requirement you could choose not
to get EV to create the system mailbox for you.
The same would also be true for V6 but unfortunately we now need this right by default even if you want to create the mailbox
manually!
This is because, for v6, we changed the format of the system mailbox to EnterpriseVault(EXCHANGESERVER) from
ExterpriseVault-EXCHANGESERVER for Exchange 2000 and 2003. For customers who upgrade from v5 to v6, they could already
have a mailbox of EnterpriseVault-EXCHANGESERVER and we need to detect this and use it when creating new tasks.
Due to this, we have added code in EV 6.0 to try and figure out if a system mailbox already exists. Unfortunately, the only
way the Microsoft APIs allows us to do this is to attempt to create the mailbox and then we know if this fails that a
mailbox already exists.
Ultimately this change means we need more permissions to add a task for Exchange 2000/2003 in V6.
Description of solution
=======================
When creating a new task the user now has the choice to pick the enterprise vault system mailbox (the format of the mailbox is
not specified) or a chosen mailbox. If the user selects the Enterprise Vault system mailbox the Enterprise Vault will only then
go off and check if the system mailbox exists - it will not do it any earlier.
Files updated
=============
The below files should all be placed in the Enterprise Vault install directory (by default C:\Program Files\Enterprise Vault)
snapin.dll
directoryservice.exe
directorydb_5_viewsstoredprocs.sql
*******************NOTE************************
I checked back with support as SP1 had been released on the same day. This fix is included in SP1.
I upgraded to SP1 over the weekend and the problem has been resolved.
Finally I am still confused as to why I could not enable the server when the service account was given domain admin rights.