Get-DhcpServerv4Lease -allleases -ScopeId #myscopeIDhere | Select-Object @{expression= {$_.hostname}; label='name' } | export-CSV -notypeinformation C:dhcpLeaseLog.csv

import-module activedirectory

#get input CSV

$leaselogpath = "c:DHCPLeaseLog.csv"
Import-csv -path $leaselogpath |
#query AD for computer name based on csv log
foreach-object `
{
   $NameResult = Get-ADComputer -Filter *
   If ($NameResult -eq $null) {$RogueSystem = $_.name}
   $RogueSystem | Out-File C:DHCPRogueClients.txt -Append
   $RogueSystem = $null

}
Get-Content C:DHCPRogueClients.txt | Select-Object -Unique | Out-File C:DHCPRogueClientsFinal.txt
Remove-Item C:DHCPRogueClients.txt

#send email to sysadmin
$smtpserver = #my email server IP address here
$from="abcd@abcdefg.com"
$to="sysadmin@abcdefg.com"
$subject="Non-AD joined DHCP clients"
$body= (Get-Content C:DHCPRogueClientsFinal.txt) -join '<BR>&nbsp;<BR>'
$mailer = new-object Net.Mail.SMTPclient($smtpserver)
$msg = new-object Net.Mail.MailMessage($from,$to,$subject,$body)
$msg.IsBodyHTML = $true
$mailer.send($msg)