List email forwarding O365

get-mailforward.ps1

$Mailboxes = Get-Mailbox -ResultSize Unlimited
ForEach ($Mailbox in $Mailboxes)
{
    $MailboxWithRule = Get-InboxRule -Mailbox $Mailbox.Alias |
    where 
    {
        ($_.RedirectTo -ne $null) -or ($_.ForwardTo -ne $null) -or ($_.ForwardAsAttachmentTo -ne $null)
    }
    if ($MailboxWithRule -ne $Null)
    {
        Write-Host "Brevlådan $($Mailbox.PrimarySmtpAddress) har dessa regler:" $MailboxWithRule | 
        fl Name, Identity, RedirectTo, ForwardTo, ForwardAsAttachmentTo
    }
}

From https://www.cert.se/2018/06/vag-av-natfiske-mot-e-postkonton-i-office-365