I have installed Exchange 2010 in our test environment and had problems getting the mailbox role to install - I think this is the root cause of the problems I'm having. I did get it to install finally by uninstalling all Exchange roles and then reinstalling but I did not clean up AD after uninstalling. Now, my database is dismounting at some point during the night and will not re-mount - the Information Store service stops and will not restart. The only way I've gotten it to restart is to power down the server & bring it back up (a restart doesn't do it). Errors in the event log point Active Directory and to not having arbitration mailboxes set up. When I ran setup /preparead initially, it was done from the Schema master which is in a different domain than Exchange. Exchange is in a child domain. The System Accounts (FederatedEmail, SystemMailbox, DiscoverySearch) are seen in ADUC for the root domain in the Users container however, they do not have mailboxes attached to them. I have attempted to enable the mailboxes from Exchange Management Shell (after setting my scope to EntireForest) and get this error: [PS] C:\Windows\system32>enable-mailbox -Arbitration -Identity "FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042" This task does not support recipients of this type. The specified recipient root.domain/Users/FederatedEmail.4c1f4d8b-8179- 4148-93bf-00a95fa1e042 is of type UserMailbox. Please make sure that this recipient matches the required recipient type for this task. I'm hoping that when I install this for real in my production environment that I don't have these same issues but I need to figure out how to get the security set up across the domains before I get to the production install date of 8/9. How can I get the arbitration mailboxes set up for these users? Should I recreate the system account users in the child domain?

Hi, Please deleted the arbitration,discovery mailbox and FederatedEmail using ADSIEDIT by following the below steps: 1)Open ADSIEDIT.msc,connect to the default naming contest 2)navigate to the users container and in the right hand side,right click and delete the following arbitration and discovery mailbox respectively “SystemMailbox{GUID}” “SystemMailbox{GUID}” "DiscoverySearchMailbox{GUID}" "FederatedEmail.GUID" 3)Run setup/preparead to recreate both the arbitration and discovery mailbox 4)Enable both the arbitration and discovery mailbox by following the below step. i) Enable-Mailbox –Arbitration –Identity “SystemMailbox{GUID}” ii)Enable-Mailbox –Arbitration –Identity “SystemMailbox{GUID}” iii)Enable-Mailbox -discovery -identity "DiscoverySearchMailbox{GUID}" iv)Enable-Mailbox -discovery -identity "FederatedEmail.GUID" If the issue persists, please post the error log relating to Information service.