Mobile Device Access Rules

Well, after trouble shooting using CoPilot, I have been trying to use the following scripts. However, the import never finishes.

Retrieve mobile list first

$mailboxes = Get-Mailbox -ResultSize Unlimited

$devices = @()
foreach ($mailbox in $mailboxes) {
    $devices += Get-MobileDeviceStatistics -Mailbox $mailbox.Alias | Select-Object DeviceID, DeviceModel, DeviceOS, LastSuccessSync
}

$devices | Export-Csv -Path "C:\AllowedDevices.csv" -NoTypeInformation

Import Allowed devices

$mailboxes = Get-Mailbox -ResultSize Unlimited

$allowedDevices = Import-Csv -Path "C:\AllowedDevices.csv"
foreach ($mailbox in $mailboxes) {
    foreach ($device in $allowedDevices) {
        try {
            Set-CASMailbox -Identity $mailbox.Alias -ActiveSyncAllowedDeviceIDs $device.DeviceID
        } catch {
            Write-Error "Failed to set allowed device for mailbox $($mailbox.Alias): $_"
        }
    }
}
Write-Output "Allowed devices import is complete."

Verify Devices are now marked allowed

Get-CASMailbox | Select-Object DisplayName, ActiveSyncAllowedDeviceIDs | Export-Csv -Path "C:\AllowedDevicesList.csv" -NoTypeInformation

Then set to Quarantine all devices after the import of allowed devices

Set-ActiveSyncOrganizationSettings -DefaultAccessLevel Quarantine