I have the same issue for sending the fax with PDF attachment.
I create the document, attachments and sends via BCS class, but i got the following issue:
No delivery to <fax number>, as part of message cannot be transferred
Message no. XS811
The message could not be delivered to recipient 6504612397 as part of the message could not be transferred.
Processing was ended normally.
Additional information of the node used (in the system language of the node):
Part of the message could not be transported all the way to recipient <fax number>. This is usually due to particular binary attachments. Check the message and remove oversized attachments and attachments that require special coding, for example.
The following is my code:
lr_send_request = cl_bcs=>create_persistent( ).
lr_document = cl_document_bcs=>create_document(
i_type = gc_doc_type_raw
i_text = it_message_body
i_subject = iv_subject ).
PERFORM get_attachments USING it_invoice_send
LOOP AT lt_attachments INTO ls_attachment.
lv_attachment_subject = ls_attachment-subject.
i_attachment_type = ls_attachment-doc_type
i_attachment_subject = lv_attachment_subject
i_att_content_hex = ls_attachment-cont_hex ).
CATCH cx_document_bcs INTO lx_document_bcs.
MESSAGE e005(zzfi_coll_enh) RAISING add_attachment_failed.
lr_send_request->set_document( lr_document ).
lr_sender = cl_sapuser_bcs=>create( sy-uname ).
lr_send_request->set_sender( lr_sender ).
lr_recipient = cl_cam_address_bcs=>create_fax_address(
i_country = iv_fax_country
i_number = iv_fax_number ).
i_recipient = lr_recipient
i_express = gc_flg_x ).
i_with_error_screen = gc_flg_x
result = ev_result ).