how to send automated emails from exchange server using PS

Hi, we are making automated scripts to send a text file with some mail addresesses to another company to inject those mails address into her exchange server.

The PS script what we use are this:

<#
script de automatización de envío de correo
Desarrollado en el Dpto de Operaciones Soluciones IT (c) 2014
Version 1.00
#>

Clear-Host

Write-Host "Script de envío de archivo de contactos" -ForeGroundColor Magenta
Write-Host "Creado por Alpha Systems S.R.L. (c) 2014" -ForeGroundColor Magenta
Write-Host " "
Write-Host " "<#
Solicitamos los datos para el envío de los correos
#>

Write-Host -NoNewLine "Ingrese el fqdn del dominio de correo: " -ForeGroundColor Yellow;$Suffix=Read-Host
Write-Host -NoNewLine "Ingrese el nombre de nuestro servidor Exchange: "-ForeGroundColor Yellow; $Server=Read-Host
Write-Host -NoNewLine "Ingrese la dirección de correo destino: "-ForeGroundColor Yellow;$Receipt_Mail_Address=Read-Host
Write-Host -NoNewLine "Ingrese la dirección de correo remitente: "-ForeGroundColor Yellow;$Sender_Mail_Address=Read-Host
Write-Host " "
Write-Host " "<#
Armamos el correo electrónico y lo enviamos
#>

$filename=“c:\Sync\Contacts-"+$Suffix+".txt”

$msg=new-object Net.Mail.MailMessage
$att=new-object Net.Mail.Attachment($filename)
$smtp=new-object Net.Mail.SmtpClient($Server)

$msg.From=$Sender_Mail_Address
$msg.To.Add($Receipt_Mail_Address)
$msg.Subject = “Correo automatizado – Contacts-"+$Suffix+".TXT”
$msg.Body=“Envío automatizado del archivo Contacts-"+$Suffix+".TXT”
$msg.Attachments.Add($filename)

$smtp.Send($msg)
Write-Host "Enviando Correo automatizado, por favor espere ... " -ForeGroundColor Green
Write-Host " "
Write-Host " "
Write-Host "Correo enviado" -ForeGroundColor Green

In the script we are asking for the name of the server, the sender and destination mail address.

In exchange Server 2010 this PS script works fine, but in Exchange 2013 SP1 does not work, we receive the following error message

Exception calling "Send" with "1" argument(s): "Mailbox unavailable. The server response was: 5.7.1 Unable to relay"
At C:\sync\RobotSendAutoMail.ps1:44 char:1+ $smtp.Send($msg)+ ~~~~~~~~~~~~~~~~+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException+ FullyQualifiedErrorId : SmtpFailedRecipientException

We need what this script works again in Exchange 2013

Raulito