$mail = new PHPMailer();
$mail->IsSMTP();                                      // set mailer to use SMTP
$mail->Host = "smtp1.example.com;smtp2.example.com";  // specify main and backup server
$mail->SMTPAuth = true;     // turn on SMTP authentication
$mail->Username = "jswan";  // SMTP username
$mail->Password = "secret"; // SMTP password
 $mail->From = "from@example.com"; $mail->FromName = "Mailer";
foreach($to as $to_add){ $mail->AddAddress($to_add);                  // name is optional
} $mail->AddReplyTo("info@example.com", "Information");
$mail->WordWrap = 50;                                 // set word wrap to 50 characters
$mail->AddAttachment("/var/tmp/file.tar.gz");         // add attachments
$mail->AddAttachment("/tmp/image.jpg", "new.jpg");    // optional name
$mail->IsHTML(true);                                  // set email format to HTML
 $mail->Subject = "Here is the subject"; $mail->Body    = "This is the HTML message body <b>in bold!</b>"; $mail->AltBody = "This is the body in plain text for non-HTML mail clients";
if(!$mail->Send()) {   echo "Message could not be sent. <p>";   echo "Mailer Error: " . $mail->ErrorInfo;   exit; }

echo "Message has been sent";

Araştırma olarak php biliyorsanız php smtp multiple send emails gibi birşey yazarak googleye sonuçlar bulabilirsiniz. iyi günler.