Attachments are not sent via internal external EDX or XML output i.e.
SAP Business ByDesign
Reproducing the Issue
Use XML as output for any output and attach an attachment. Attachments are not considered.
Attachments are not sent.
This is a known Limitation confirmed by the OM Framework Team.
What you can try is,
add a KUT Field or extension field
here maintain the link from the attachment via PDI-Partner Solution.
The attachment will be then part of the XML itself.
Attachments, XML Output, Internal-External EDX, Attachments. , KBA , AP-RC-OUT , Output Management , How To