Migration of Active directory and Office 365 to another AD and office 365 (retaining external email)

Copper Contributor

Hi all,


I have been asked to complete an active directory migration for a customer for a company they have purchased. 

The current setup is:

  • One domain that currently has an active directory domain original-domain.local
  • ADSync to sync mailboxes to office365 using original-domain.com as their accepted domain.
  • Has one drive data that needs to be migrated
  • Has SharePoint sites that need to be migrated

The users need to be migrated to:

  • Another domain called other-domain.local
  • other-domain.local has an office 365 setup using ADsync to sync their mailboxes
  • other-domain.com as their accepted domain

I have planned on using ADMT to move the accounts to the new domain and have the following phases for the migration steps:

  • Active Directory Preparation
  • Device Migration Preparation
  • Group Account Migration
  • Migration tool Preparation (ADMT)
  • Service Account Migration
  • User Account Migration
  • Workstation local profile translation
  • Workstation Migration

The customer wants to:

Migrate the users from the original-domain.local to the other-domain.local and migrate the mailboxes over but retain the original-domain.com accepted domain and complete this is batched stages instead of a cutover.

in the past, I could do this by routing mail via an exchange server to the other exchange and then migrate the users over but with office 365 I am not sure how this fits into ADMT.

when do we start mailboxes migrations and at what stage during the ADMT process would this happen?

Also, how do we marry up mailboxes with the correct account? i.e. do you first migrate the users, then create new mailboxes in the other-domain.com tenancy then sync the mail over?

and is it possible to keep mail flow from the other-domain.com to the original-domain.com or visa versa whilst in the process of the migration?

Can it be staged or does it need to be a cutover?

has someone completed a similar migration recently with office 365 and active directory that could provide an overview of what steps are required to complete this and in what order?


1 Reply

@dustinduxbury Could you move your post to the Azure Active Directory forum? This doesn't seem to be related at all to Microsoft Stream.


AAD Identity forum: Azure Active Directory Identity - Microsoft Tech Community