Migrating old tenant users & groups to other tenant look for conflicts

Question

My work has purchased another business that has an Office 365 tenant. I want to migrate those user and groups etc over to our current Office 365 tenant. Before doing that I need to compare UPN, email addresses etc for conflicts. For example, we would currently have an accounting@business1.com and the other tenant may have accounting@business2.com
When bringing that over I will need to rename the one we are migrating from to example usa.accounting@business1.com

Is there a way to easily compare these for conflicts before hand? We have thousands and thousands of groups so I can't go through manually and check off that many groups and names. I think I would be there forever.
Does anyone know an easy way to do this? Is there a program out there or something else that could help?

Appreciate your responses.

Answer 1

Hi,

You can use powershell Az module to create a powershell script.

Get-AzADUser will give you all users in a particular tenant and then you can compare in whatever way you want.

Hope this helps

Answer 2

@Matt Holko

Connect to the purchased tenant, run commands below on it(Those two files will be used to compare on the new tenant):

Get-Mailbox -RecipientTypeDetails UserMailbox -ResultSize unlimited | select PrimarySmtpAddress |  Export-Csv c:/temp/users.csv -NoTypeInformation  
  
Get-DistributionGroup -ResultSize unlimited | select PrimarySmtpAddress |  Export-Csv c:/temp/groups.csv -NoTypeInformation  

Connect to new tenant, then run script below on it(Save script blow into a .PS1 file):
Compare mailboxes:

$users = Import-Csv c:/temp/users.csv  
  
foreach ($user in $users){  
    $temp = $user.PrimarySmtpAddress.Split('@')[0]  
    If(Get-Mailbox $temp -erroraction 'silentlycontinue'){  
        Write-Host $temp "exist in this tenant"  
    }  
}  

Compare groups:

$users = Import-Csv c:/temp/Groups.csv  
  
foreach ($user in $users){  
    $temp = $user.PrimarySmtpAddress.Split('@')[0]  
    If(Get-DistributionGroup  $temp -erroraction 'silentlycontinue'){  
        Write-Host $temp "exist in this tenant"  
    }  
}  

If there exist a mailbox or group using the same prefix for email address, you will get a result like below:

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