Email always sent as High priority using CL_BCS

I'm using the BCS classes to send email to trade partners. Some trade partners receive the emails as high priority (Ex. xxxx@yahoo.com)even though the priority is set to low. I am creating the document as follows:

document = cl_document_bcs=>create_document(

i_type = 'RAW'

i_importance = '9'

i_text = lt_textbody

i_length = lv_len_textbody

i_subject = cv_subject ).

This is occurring whether I set i_importance = 1 thru 9.

Is there possibly a SAPConnect setting that controls this?