Thanks in advance for the help.
I have two on premises Active Directory forests, ForestA and ForestB. Azure AD Connect is installed on a server in ForestB and has connectors synchronizing both ForestA and ForestB to Office 365. I also have an Exchange hybrid server in ForestA that is being used to manage mailboxes in Office 365 and one in ForestB. Each user in ForestA has a mailbox in O365 and is matched using ms-ds-consistencyGUID (there are no on-premises mailboxes).
I need to migrate all AD user accounts from ForestA to ForestB. When I do this, I need to be sure that the mailbox is not deleted and the migrated user account in ForestB is matched to the O365 mailbox via directory synchronization.
How do I do this? Please note that I need to migrate 5000+ accounts so it will need to be done in batches and I can't disable dirsync at any point. I will use Quest Migration Manager for AD.
