Create mail enabled security group based on O365 Unified group

group copy.ps1

## Option 1 - This can be used to be prompted for credentials
$UserCredential = Get-Credential

## Option 2 - If you really want to automate the script, you will
## want to hard code the credentials to log into Azure AD.
# $User = "<ADMIN USER>"
# $PWord = ConvertTo-SecureString -String "<PASSWORD>" -AsPlainText -Force
# $UserCredential = New-Object -TypeName "System.Management.Automation.PSCredential" -ArgumentList $User, $PWord

## Create the session to Exchange Online
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

## Import the Exchange Online commands
Import-PSSession $Session

## Requires the Azure AD 2.0 cmdlets
## Install-Module -Name AzureAD
Connect-AzureAD -credential $UserCredential

## Set the names for the groups
## Old Group = Office 365 Unified Group
## New Group = The new Mail enabled security group that will be created.
$oldGroupName = "Sales Group"
$newGroupName = "My Group"

## Get references to old and new group.
## New group may be null if it hasn't been created yet.
$oldGroup = Get-AzureADGroup -SearchString $oldGroupName
$newGroup = Get-AzureADGroup -SearchString $newGroupName

if($newGroup -eq $null)
{
    ## Update the managedby and PrimarySmtpAddress addresses
    ## Managed by = owner of group
    ## these can be changed later in the Exchange Online Admin portal
    New-DistributionGroup -Name $newGroupName -Type "Security" -ManagedBy "asaxton@guyinacube.com" -PrimarySmtpAddress "mygroup@guyinacube.com"

    Write-Output "New group created!"

    ## Get reference to new group
    $newGroup = Get-AzureADGroup -SearchString $newGroupName
}
else
{
    Write-Output "New group already exists!"
}

$oldGroupMembers = Get-AzureADGroupMember -ObjectId $oldGroup.ObjectId -All $true
$newGroupMembers = Get-AzureADGroupMember -ObjectId $newGroup.ObjectId -All $true

## Add old members to new group
## Check to make sure the member doesn't already exist.
Foreach ($member in $oldGroupMembers) 
{
    if($newGroupMembers -notcontains $member)
    {
        Add-DistributionGroupMember -Identity $newGroupName -Member $member.UserPrincipalName
        
        $message = "New group does not contain member - "
        $message += $member.UserPrincipalName
        Write-Output $message
    }
    else 
    {
        $message = "New group contains member - "
        $message += $member.UserPrincipalName
        Write-Output $message
    }
}

## list out members of the new group
Get-AzureADGroupMember -ObjectId $newGroup.ObjectId -All $true

Hi Team,

I got the same error when I am trying to add a user to mail-enabled security groups.
Can you help me to fix these issues?

Regards,
Kamaraj.P