I was assign a print program for PO and what i did for the output type was to send auto PO to user and sender and information.
But what the functional requested more that is when the sender email has received he wants a pop up which is to say email have been sent to you.
So using the FM CALL FUNCTION 'SO_DOCUMENT_SEND_API1'
and any error occured it will pop up in Send Express Information (pop up)

Configuration to be made in Shared office settings
- Tcode :- SO16
- Mail sy. grp
Select No Mail System Group