OSB email - forcing multipart/mixed - email

Question

I am sending email using a OSB (11.1.1.6) service.
Some email clients do not pick up the attachments.
We have narrowed down the problem down to MIME Content-Type.
Going through OSB it sets the Content-Type to multipart/related. In order to get it to work (we tested this using ncat) we need to set the Content-Type to multipart/mixed.
I cannot however find any way to force OSB to set it to multipart/mixed.
This message does not display the attachment on some clients:
From: <nothing#example.com>
To: nothing#example.com
Message-ID: <xxx>
Subject: Subject 123
MIME-Version: 1.0
Content-Type: multipart/related; boundary="MIME_Boundary";
start=1389578236803081255-2926c9b7.148d69bfba8.7396
Return-Path: nothing#example.com
--MIME_Boundary
Content-ID: 1389578236803081255-2926c9b7.148d69bfba8.7396
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit
<h1>Head</h1>
<p>Paragraph <b>bold</b></p>
--MIME_Boundary
Content-Type: text/plain; name="TEST.txt"
Content-Transfer-Encoding: base64
Content-Description: TEST.txt
Content-Disposition: attachment; filename="TEST.txt"
VGVzdGluZyAxMjM=
--MIME_Boundary--
This message displays the attachment:
From: <nothing#example.com>
To: nothing#example.com
Message-ID: <xxx>
Subject: Subject 123
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="MIME_Boundary";
start=1389578236803081255-2926c9b7.148d69bfba8.7396
Return-Path: nothing#example.com
--MIME_Boundary
Content-ID: 1389578236803081255-2926c9b7.148d69bfba8.7396
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit
<h1>Head</h1>
<p>Paragraph <b>bold</b></p>
--MIME_Boundary
Content-Type: text/plain; name="TEST.txt"
Content-Transfer-Encoding: base64
Content-Description: TEST.txt
Content-Disposition: attachment; filename="TEST.txt"
VGVzdGluZyAxMjM=
--MIME_Boundary--
As you can see the only difference is the Content-Type.
So how do I force OSB to set the Content-Type to multipart/mixed ?

Answer 1

You can set the Transport Header Content-Type. I assume you are using the routing to call the BS service which has email configuration. From Proxy, where you are routing, in the request actions, add Communication > Transport Headers. From the drop down, select emails >> Content-Type.

Answer 2

After some communication with Oracle support we were pointed to apply patch 12585136.
This was one of the bugs fixed for OSB 11.1.1.7 (link)
12585136 - The Email transport generates multipart/related emails and not mulitpart/mixed
After we have applied and tested the patch I will update this answer with more feedback.