M365 Domain Removal

Prerequisites

• M365 Admin Access: You need to have the necessary admin permissions

• Powershell : Install the Microsoft Azure Active Directory Module and Exchange Online Management Module for Windows PowerShell

Important Notes

• Always ensure you have backups or have planned for any required changes before removing a domain.

• Before running this script in a production environment, test it in a safe, non-production environment to avoid accidental data loss or service disruption.

# Output will be added to C:temp folder

Start-Transcript -Path "C:tempRemove-M365Domain.log" -Append

#Get values for input parameters

$olddomain =”joseph.com”

$Newdomain=“ludwig.com”

#Connect to MsolService

Import-Module MsOnline

$credential = get-credential

Connect-MsolService -Credential $credential

#Connect to Exchange Online:

$ExchangeSession = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri “https://outlook.office365.com/powershell-liveid/” -Credential $credential -Authentication “Basic” –AllowRedirection

Import-PSSession $ExchangeSession

#Change the UserPrincipalName for all Microsoft 365 users

$users=Get-MsolUser -domain $olddomain

$users | Foreach-Object{

$user=$_

$UserName =($user.UserPrincipalName -split “@”)[0]

$UPN= $UserName+“@”+ $Newdomain

Set-MsolUserPrincipalName -UserPrincipalName $user.UserPrincipalName -NewUserPrincipalName $UPN

write-Host “The UserPrincipalName for all Microsoft 365 users has been successfully updated”

#Change Email Addresses for all Microsoft 365 Mailboxes

$Users=Get-Mailbox

$Users | Foreach-Object{

$user=$_

$UserName =($user.PrimarySmtpAddress -split “@”)[0]

$SMTP =“SMTP:”+ $UserName +“@”+$Newdomain

$Emailaddress=$UserName+“@”+$Newdomain

$user | Set-Mailbox -EmailAddresses $SMTP -WindowsEmailAddress $Emailaddress -MicrosoftOnlineServicesID $Emailaddress

}

write-Host “The email addresses for all Microsoft 365 mailboxes have been successfully updated”

#Change Email Addresses for all Distribution Groups

$Groups=Get-DistributionGroup

$Groups | Foreach-Object{

$group=$_

$groupname =($group.PrimarySmtpAddress -split “@”)[0]

$SMTP =“SMTP:”+$groupname+“@”+$Newdomain

$Emailaddress=$groupname+“@”+$Newdomain

$group |Set-DistributionGroup -EmailAddresses $SMTP -WindowsEmailAddress $Emailaddress -MicrosoftOnlineServicesID $Emailaddress

}

write-Host “The email addresses for all Distribution Group have been successfully updated”

#Change Email Addresses for all Dynamic Distribution Groups

$Groups=Get-DynamicDistributionGroup

$Groups | Foreach-Object{

$group=$_

$groupname =($group.PrimarySmtpAddress -split “@”)[0]

$SMTP =“SMTP:”+$groupname+“@”+$Newdomain

$Emailaddress=$groupname+“@”+$Newdomain

$group |Set-DynamicDistributionGroup -EmailAddresses $SMTP -WindowsEmailAddress $Emailaddress -MicrosoftOnlineServicesID $Emailaddress

}

write-Host “The email addresses for all Dynamic Distribution Group have been successfully updated”

#Change Email Addresses for all M365 Groups

$Groups=Get-UnifiedGroup

$Groups | Foreach-Object{

$group=$_

$groupname =($group.PrimarySmtpAddress -split “@”)[0]

$SMTP =“SMTP:”+$groupname+“@”+$Newdomain

$Emailaddress=$groupname+“@”+$Newdomain

$group |Set-UnifiedGroup -EmailAddresses $SMTP -WindowsEmailAddress $Emailaddress -MicrosoftOnlineServicesID $Emailaddress

}

write-Host “The email addresses for all M365 Group have been successfully updated”

#Remove the old Microsoft 365 domain

Remove-MsolDomain -DomainName $olddomain -Force

write-Host “The old Microsoft 365 domain has been successfully removed.”

Stop-Transcript