I use Custom Soap Sampler to attach files to SOAP requests in JMeter. I use XML version 1.0 and SOAP version 1.1. I selected attachment and set content ID to ref1 and set type to resource.
SOAP envelope contains reference to file here:
<data><xop:Include href="cid:ref1" xmlns:xop="http://www.w3.org/2004/08/xop/include"/></data>
I get error message as response:
Message part {http://www.ebxml.org/namespaces/messageHeader}Manifest was not recognized. (Does it exist in service WSDL?)
I checked raw request and found, it is different than standard ones. It starts with following lines:
------=_Part_6_231845394.1524218533567 Content-Type: text/xml; charset=utf-8