Release of purchase order- Mail isssue

Hi Everyone,

At the time of Po release we are triggering WF. As a part of WF we have a task TS20000168 (Release of purchase order effected) in this task an email will be sent to the po creator with work item "Purchase order xxxxxxxx released Execute Work Item Back to Overview" but I would like to convert this as a simple mail not as a work item" I had tried debugging this task using TCODE:SWUS but not able to find out the place where exactly this e-mail is triggering.Please help me.

Thanks in advance