Hi,
better option is to convert your spool request to PDF and 
send it

call function 'CONVERT_ABAPSPOOLJOB_2_PDF'
exporting
src_spoolid = mi_rqident
no_dialog = c_no
dst_device = c_device
importing
pdf_bytecount = gd_bytecount
tables
pdf = it_pdf_output
exceptions
err_no_abap_spooljob = 1
err_no_spooljob = 2
err_no_permission = 3
err_conv_not_possible = 4
err_bad_destdevice = 5
user_cancelled = 6
err_spoolerror = 7
err_temseerror = 8
err_btcjob_open_failed = 9
err_btcjob_submit_failed = 10
err_btcjob_close_failed = 11
others = 12.
check sy-subrc = 0.
* Transfer the 132-long strings to 255-long strings
loop at it_pdf_output.
translate it_pdf_output using ' ~'.
concatenate gd_buffer it_pdf_output into gd_buffer.
endloop.
translate gd_buffer using '~ '.
do.
it_mess_att = gd_buffer.
append it_mess_att.
shift gd_buffer left by 255 places.
if gd_buffer is initial.
exit.
endif.
enddo.

then call FM after populating attachment data

call function 'SO_DOCUMENT_SEND_API1'
exporting
document_data = w_doc_data
put_in_outbox = 'X'
sender_address = ld_sender_address
sender_address_type = ld_sender_address_type
commit_work = 'X'
importing
sent_to_all = w_sent_all
tables
packing_list = t_packing_list
contents_bin = t_attachment
contents_txt = it_message
receivers = t_receivers
exceptions
too_many_receivers = 1
document_not_sent = 2
document_type_not_exist = 3 

In close_form function module there is option of getting 
output in OTF form. Go to se37 and in table tab convert 
that table to hex (BIN) format and pass it to objbin and 
send normal mail.