Child domain lost - How best to disconnect/disable mailboxes with no writable AD

Ben Owens
Occasional Contributor

The root AD forest has multiple sub domains, for example contoso.com is root, child domains, sub1.contoso.com, sub2.contoso.com etc.


Exchange 2016 servers is installed into the root domain, contoso.com with prepearealldomains, so allows mailboxes to be associated AD user objects in the child domains.


There was a issue encountered resulting in no writable DC for child domain sub1.contoso.com.  In addition the mailbox database which holds the mailboxes for these child domain is not recoverable.


At the moment, the rest of Exchange is functioning okay.


I want to run Disable-Mailbox, Remove-Mailbox to delete mailbox for the sub1.contoso.com mailbox accounts, or run Set-Mailbox with a -ForwardingSMTPAddress, in order to route emails destined for the child domain users elsewhere.  Unfortunately each of these options require the ability to access the mailbox database in question or a child dc in sub1.contoso.com.


Does anyone know how I can set the ForwardingSMTPAddress for these child user accounts mailboxes, or disable/disconnect the mailbox for these users in this scenario?