Published by Migration Monster   https://www.migration-monster.com

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There may be times when you need to move your mailboxes to a new Office 365 tenant and need to take your domain with you, for example, a company buyout. This means you will need to decommission the domain on the current tenant and move it to another. The process below gives you steps on how to achieve this goal.


This type of migration will require some downtime as Microsoft do not allow a domain to exist on more than one tenant at a time.



  • First we need to start preparing the destination tenant account so it’s ready to receive data from your current tenant. Add your domain\s to the destination tenant but at this stage do not verify it\them yet. You will need to also add the requested text record to your DNS to allow it to replicate.
  • Within your DNS setup change the TTL of your MX records to 1 minute
  • Using the default Office 365 domain ( <organization_name>.onmicrosoft.com ) setup your users account on your new destination tenant and assign a license.
  • Make a note of the primary and alias email addresses configured for each user on the source.
  • Now login to your account on our Migration Monster system and setup a migration project using both the source and destination URL’s as https://outlook.office365.com . You will need to decide if you plan to use admin credentials on the source and destination or use the users credentials to access each mailbox. We recommend using admin credentials with the admin accounts .onmicrosoft.com (as the primary) domain for authenticating source and destination as this allows the moving of all vanity domains you may have between tenants without affecting the migration project.
  • Populate the Migration Monster project with the mailboxes you would like to migrate and then start your first Migration Pass.
  • Once the pass has completed and you are ready to start your migration Change your MX records to an unreachable destination so that email starts to queue within the sending mail server. You now have a maximum of 24 hours to complete your migration before email will start to be rejected and NDR (non-delivery reports) will be sent to the sender and emails dropped. After 4 hours’ senders may receive a DSN (Delivery status notification) informing of the message delay. You may prefer to put in place a backup MX provider to hold the emails for longer and with no DSN or NDR messages while the migration takes place.
  • Once the email has been prevented from entering you old tenant account start a second migration using Migration Monster to copy and residual items over on to your new Office 365 tenant. Check to make sure that all required mailboxes and content have been migrated as specified.
  • To allow you to remove the domain from the source tenant, now delete all users, contacts and groups from the source Office 365 account
  • Now remove the domain from the source tenant and wait an hour for your changes to replicate.
  • Now verify your domain\s on the new tenant that you configured the DNS for in stage 1. If the domain refuses to verify contact Microsoft support. It is quite common for Microsoft to have to manually de-provision before you are able to verify correctly.
  • Once the domains have been added, for each user, you will now need to setup the required email addresses for the domain\s you have verified.  Remember to setup alias’s as well as the primary email address.
  • Now wait for one hour to allow the changes made to replicate through Microsoft’s systems.
  • Now point your primary MX record back to Office 365 and decommission the backup MX provider if you put this in place.



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Published by Migration Monster   https://www.migration-monster.com