hi at the momment we have a resource domain setup, there is a trust between domain a-b and the resource domain, our link link mail boxes are set to auth with domain A how can i change it so there accouns are set to auth with domain B cheers Mark

Hi Mark, I would like to know whether you want to let the user on Domain B to log on the mailboxes on resource domain instead of the original user on domain A. If I am correct, I suggest that you can use the following command to change the user associated with the mailbox: Set-mailbox mailbox name linkeddomaincontroller dc name of domain B linkedmasteraccount domainB\username Linkedcredential:{get-credential domainB\admin} Note: The domainB\username represent the user in domain B which you would like to let him access the mailbox. The domainB\admin account need to have sufficient permission to access the DC of domain B which you indicated. After modifying the above two properties of the mailbox, the user B should be able to login and access the mailbox. Nevertheless, you also need to modify some related property such as Mailbox display name, Distinguished Name as so on. You can get the mailbox properties by running the following command to check which properties need to modify: Get-mailbox mailbox name |fl Mike