outlook doesn't recognise base64 encoded attachment (gmail does) - php

Question

I'm learning how to attach a base64 encoded image to an email generated in php and sent using AWS. Sending to my gmail address it seems to work perfectly but sending to an account picking up with outlook 2003, there is an attachment but it's 142B.
It seems to me that this is either an outlook settings problem or that gmail is forgiving an error of mine that outlook doesn't.
$pName = "frank";
$pSubject = "test email";
$pToEmail ="me#gmail.com"; // alternate = "me#work.com" picked up on outlook 2003
$attachedFile = '/Code/test.jpg';
$check = getimagesize($attachedFile);
$message = "To: $pName <". $pToEmail .">\n";
$message .= "From: Frank <franki#franki.co.uk>\n";
$message .= "Subject: ".$pSubject."\n";
$message .= "MIME-Version: 1.0\n";
$message .= 'Content-Type: multipart/mixed; boundary="frankis_image_boundary_02122016"';
$message .= "\n\n";
$message .= "--frankis_image_boundary_02122016\n";
$message .= 'Content-Type: text/plain; charset="utf-8"';
$message .= "\n";
$message .= "Content-Transfer-Encoding: 7bit\n";
$message .= 'Content-Disposition: inline';
$message .= "\n\n";
$message .= "Dear new tester,\n\n";
$message .= "Attached is the file you requested.\n";
$message .= "\n\n";
$message .= "--frankis_image_boundary_02122016\n";
$message .= "Content-ID: <test.jpg#domain.com>\n";
$message .= 'Content-Type: '.$check['mime'].'; name="test.jpg"';
$message .= "\n";
$message .= "Content-Transfer-Encoding: base64\n";
$message .= 'Content-Disposition: attachment; filename="test.jpg"';
$message .= "\n";
$message .= base64_encode(file_get_contents($attachedFile));
$message .= "\n";
$message .= "--frankis_image_boundary_02122016--\n";
$sendMsg['RawMessage']['Data'] = (string)base64_encode($message);
$sendMsg['RawMessage']['Source'] = "franki#franki.co.uk";
$sendMsg['RawMessage']['Destinations'] = array($pToEmail);
//$client appropriately set up here
$result = $client->sendRawEmail($sendMsg);
Many searches here discuss problems embedding images in outlook, I just want it to send as an attachment. Any solutions or suggestions appreciated.