EDIT: maybe you just need to send binary attachment?
With cl_document_bcs=>string_to_solix you can set codepage and get binary content + size => pass that as 'BIN' attachment.
With this you can change e-mail codepage:
Not sure if it is propper way to do, but works for me.
DATA: lo_head type REF TO cl_bcs_objhead.
lo_head = cl_bcs_objhead=>create( ).
lo_head->set_format( lo_head->gc_asc ). "ASC for text document
lo_head->set_codepage( '1100' ). "1100 = ISO-8859-1 ? is it LATIN1 ?
Create document with this method:
lo_document = cl_document_bcs=>create_document(
i_type = 'RAW'
i_header = lo_head->MT_OBJHEAD
"also pass text, subject etc...
).
In e-mail "internet header" i can read:
Content-Type: text/plain; charset="iso-8859-1"
instead of default:
Content-Type: text/plain; charset="utf-8"