$users = @(Get-ADUser -Filter "userPrincipalName -like '*$suffix'" -SearchBase $OU)
$users | foreach-object {
    $upn = $_.userprincipalname.replace("$suffix","$newsuffix")
    logwrite “changed the UPN suffix for : $UPN on $date"
    set-aduser $_ -userprincipalname $upn
}

if($users.Count -gt 0) {
    send-mailmessage -to "User01 <user01@example.com>" -from "User02 <user02@example.com>" -subject "Users has been changed" -Attachments "c:logs$($currentuser).log”
}

Get-ADUser -Filter "userPrincipalName -like '*$suffix'" -SearchBase $OU |
   foreach-object {
     $upn = $_.userprincipalname.replace("$suffix","$newsuffix")
        $logfile += “changed the UPN suffix for : $UPN on $date`n"
          set-aduser $_ -userprincipalname $upn
     }

if($logfile)
{
$logfile | out-file <filename>
send-mailmessage -to user@dmain.com -from person@domain.com -subject $subject -body $logfile
}