Hi Ricardo
Standard adapter modules only work on the main payload, unless you swap it with the swap bean. Since for your case using swap bean is out of the question due to multiple attachment, a possibility would be adding additional code in your custom module as suggested by Amit.
You can try it with the following logic that iterates over all the attachment and changes the content type.
Iterator iter = msg.getAttachmentIterator();
while(iter.hasNext()) {
XMLPayload attachment = (XMLPayload) iter.next();
attachment.setContentType("application/xml");
}
Rgds
Eng Swee