Function module falling SO_NEW_DOCUMENT_SEND_API1

Hi All,

When iam using the function module SO_NEW_DOCUMENT_SEND_API1 it is giving the sy-subrc as 2 .iam using this code

*Collect the Email,Message type Message body present in the internal table to send an email

WA_MAILDATA-obj_descr = IS_BACKMON-Message_Subject.

*Collect the mailid and reciver type to send an email

WA_RECEIVER-receiver = 'Emailid'.

WA_RECEIVER-rec_type = 'U'.

WA_RECEIVER-com_type = 'INT'.

APPEND WA_RECEIVER to i_RECEIVER.

*Display the context of the message

is_contents_txt = 'Test'.

APPEND is_contents_txt to i_contents_txt.

clear i_contents_txt.

*Send an Email to a Particular person

call function 'SO_NEW_DOCUMENT_SEND_API1'

exporting

document_data = WA_MAILDATA

document_type = 'HTM'

put_in_outbox = 'X'

commit_work = 'X'

tables

OBJECT_CONTENT = i_contents_txt

receivers = i_RECEIVER

exceptions

too_many_receivers = 1

document_not_sent = 2

document_type_not_exist = 3

operation_no_authorization = 4

parameter_error = 5

x_error = 6

enqueue_error = 7

others = 8.

if sy-subrc eq 0.

Please help me if you hav answer