I am trying to use this class to send smtp mails form my server using a working email account so my script looks like this:
  ##############################################################################
  #  Project : ABG_SMTPMail                                                    #
  #  File    : ABG_SMTP_test.php                                               #
  #  V1.0.0 26/03/2006  : Initial                                              #
  #  V1.1.0 21/05/2006  : Improvements & fit to new classes                    #
  #  V1.1.1 21/05/2006  : Minor bug fixes                                      #
  #  (cy)  G. BENABOU / ABG Soft PARIS FRANCE                                  #
  #                                                                            #
  #  A PHP 4 script to test the ABG_SMTP Classes                               #
  #                                                                            #
  ##############################################################################
  // Choose (uncomment) the script you want to use (only one at a a time !!)
  require ("ABG_SMTP.inc.php");                   // Full features
  //  require ("ABG_SMTP_Lite.inc.php");              // Lightened
  /*** Definitions ************************************************************/
  $server  = "mail.mywebsite.net";    // SMTP server URL
  $login   = "sales+mywebsite.net";              // Authentification login; blank if not used
  $pwd     = "mypass";            // Authentification password (if authent.)
  $from    = "
[email protected]";  // Sender email address
  // List(comma separated) of recipients (ABG_SMTP.inc.php)
  // Unique recipient (ABG_SMTP_Lite .inc.php)
  $to      = "
[email protected]";
  // List(comma separated) of more recipients
  // $cc & $bcc used by ABG_SMTP.inc.php only; left for compatibility
  $cc      = "";
  $bcc     = "";
  $subject = "VENTA";
  $body    = "Venta $99.95 PP";
  /*** Instantiate object and run **********************************************/
  $smtp    = new ABG_SMTPMail($server);
   // Get the result of the transaction and reports
  $Result = $smtp->ob_SendMail( $login, $pwd, $from, $to, $cc, $bcc, $subject, $body);
  echo ($smtp->ob_Status);
  echo ($Result ? "Message sent succesfully!" : "Error sending message \n $smtp->ob_Error");
But for some reason I get this response: 
<220-server.mywebsite.net ESMTP Exim 4.69 #1 Sun, 31 Aug 2008 16:19:10 -0300
>HELO : localhost ? 250
<220-We do not authorize the use of this system to transport unsolicited,
Error sending message
*** Error ***
Waiting  = 250
Received = 220
Does anyone knows what to do here?
Thank you!!