在邮件中使用`addStringAttachment`和`addEmbeddedImage`到MS Outlook

Question

I have been trying to send emails with an attachment using PHPMailer. This worked fine. Then I decided to embed an image using the addEmbeddedImage-method.

Now I have a problem! The emails are received fine in gmail. But when I open the email in windows (using MS-Outlook) the attachment disappears!!

$mail = new PHPMailer;

//Server settings
$mail->SMTPDebug = 0;                       // Disable verbose debug output
$mail->isSMTP();                            // Set mailer to use SMTP
$mail->Host = $mailHost;                    // Specify main and backup SMTP servers
$mail->SMTPAuth = true;                     // Enable SMTP authentication
$mail->Username = $mailUserName;            // SMTP username
$mail->Password = $mailPassword;            // SMTP password
$mail->SMTPSecure = 'tls';                  // Enable TLS encryption, `ssl` also accepted
$mail->Port = 587;                          // TCP port to connect to

//Recipients
$mail->setFrom($mailSentFrom , $organisation);
$mail->addAddress($emailAdress, $recipientFullName);

//Attachments
$mail->addEmbeddedImage($_SERVER['DOCUMENT_ROOT'].PHP_PATH.'/library-overrides/FPDF/images/small-logo.jpg', 'logo');
$mail->addStringAttachment($attachment, "$categoryName $seasonName, $recipientFullName.pdf", 'base64', 'application/pdf');

$mail->isHTML( true );
$mail->Subject = "$categoryName $seasonName";
$mail->Body = ""; // contains html version of email (omitted for readability)
$mail->AltBody = "";

$mail->send();

Any ideas how to fix this?