Muy fácil / Very easy:
Antes de ejecutar la FM SO_NEW_DOCUMENT_ATT_SEND_API1, debemos actualizar SY-UNAME, por supuesto, el usuario que vamos a asignar debe tener asociado su e-mail correspondiente en la SU01, or ejemplo:
Before executing the FM SO_NEW_DOCUMENT_ATT_SEND_API1, we must update SY-UNAME, of course, the user that we are going to assign must have its corresponding e-mail associated in SU01, for example.
sy-uname = ls_
CALL FUNCTION 'SO_
EXPORTING
document_data
put_in_outbox
commit_work
TABLES
packing_list
object_header
contents_txt
contents_bin
receivers
EXCEPTIONS
too_many_
document_not_
document_type_
operation_no_
parameter_error
x_error
enqueue_error
OTHERS