In our evolving industry where mergers and acquisitions happen on a weekly basis its most likely that at some point you will have to migrate an email system.
In this article i will be focusing on migrating a Google Apps Domain for to another Google Apps Domain called .
At first it sounds easy, both are on Google right ? why cant we just “move” the users to the new management domain and be done with it ?
Surprise …. it cant be done, so you are stuck with a full scale migration on your hands ….
In the past, email systems were just emails, but today with google and Azure its not just emails its much more !
It includes Google Drive, MDM solutions GCP accounts etc … so planning is essential for a successful project !
My first advice, if the migration is for a company that is heavily invested in google, and its not just email, make sure you allocate a fair amount of time for this project
Here is what you need to consider before you start planning the project, These are blockers you have to take in mind and clear out :

  • Google Analytics accounts – What do i do with them ? how much time would it take to move them ?
  • GCP accounts – are my Google Apps users accounts used to login to my GCP ?
  • SSO – Do i use Google as a SAML IDP ?
  • MDM : Do you have google MDM implemented which manages your mobile devices ?
  • Team Drives – Are Team drives being used in the domain ? how much data do they hold ?
  • OAuth – which SAAS services use google for OAuth integration (Login with your google account).
  • Whats is the Number of mailboxes to be moved.
  • What is the Size of data that needs to be moved from Drive .
  • What will be destination email addresses ? would they change or stay the same, maybe hybrid  ?

As you can see, there are a LOT of considerations, so make sure you have enough time to check each and everyone of them thoroughly! (that can take a few month to clear all the blockers).

Once you get all the above questions answered you need to decide how you are going to migrate your data:

Depending on size, if you have only a few mailboxes it is possible to do it manually be exporting and importing the data, but that has a LOT of disadvantages (As you cant move all the data instantly, you will have to do it twice, once for the the bulk of the data and again after you do the cut over) so  strongly advise you to not waste time on it and use an external company for the job.

there are a couple of companies that have built in tools to migrate the data, including emails, calendars, contacts, Groups and google drive. Like CloudM or Cloud-solutions (i’m sure there are many more).

whats next :

You will need to add a secondary domain to the , say so you can set it as primary once you migrate (this will make sure your old domain is still accessible after the migration).

Plan the time to start phase 1 migration a few weeks before the cut over so you have enough time to migrate all the data (it can take from a few days to a few weeks depending on the size).

Communicate ! make sure you let the users know whats going on, you dont want anyone to be surprised that his mailbox magically disappeared .

Phase 1 Migration

This will be the mass data move to the destination domain :

Create the end users accounts in domain .
create a mapping file to show exactly which user in will move to account.
Map source and destination groups, what happens if you have and ?
start the migration, and get the data moving …

Phase 2 migration

This should probably happen on the weekend as you dont want to cause any user downtime  …

(If you are doing it on a working day, make sure you get a mail server to redirect your mx record to so you dont lose any emails in the transition)

Remove the domain registration from the old google domain, make as primary
add to the the destination google domain . (DNS validation required)
start delta migration of all the data that accumilated since the bulk move move in phase 1.

Phase 3 migration

delete all the source mailboxes.
Close the source google domain .

Small thing to remember about the google drive migration: only documents that people own will be moved, so anyone sharing their files with you will need to re-share them .

I hope this article will help you complete your google domain migration successfully !

Good Luck !


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