dlimportexport.ps1

# Export
$allGroups = Get-DistributionGroup | select Name, primarysmtpaddress

$exportlist = @()

foreach($group in $allGroups) {
    $obj = New-Object -TypeName psobject
    $obj | Add-Member -MemberType NoteProperty -Name Name -Value $group.Name
    $obj | Add-Member -MemberType NoteProperty -Name Email -Value $group.PrimarySMTPAddress

    $members = Get-DistributionGroupMember $group.Name | select Name
    $obj | Add-Member -MemberType NoteProperty -Name Members ($members | ConvertTo-Json)
    $exportList += $obj
}

$exportlist | ConvertTo-Json | Out-File '.\dlexport.json'

# Import
Set-StrictMode -Version 2

$distributionGroups = Get-Content '.\dlexport.json' | Out-String | ConvertFrom-Json

$count = 0

foreach ($dl in $distributionGroups) {
    $new = New-DistributionGroup -Name $dl.Name -OrganizationalUnit "OU" `
         -PrimarySmtpAddress ($dl.Email).Address -RequireSenderAuthenticationEnabled $false -ErrorAction SilentlyContinue

    $memberList = $dl.members | ConvertFrom-Json

    foreach ($member in $memberList) {
        write-host "Adding User $($member.Name) to $($dl.name)"
        $aduser = Get-recipient $member.Name -Erroraction SilentlyContinue

        if ([string]::IsNullOrWhiteSpace($aduser)) {
            continue
        }

        $new | Add-DistributionGroupMember -Member $aduser.Name -ErrorAction SilentlyContinue
    }
}