Hi,
There is a custom object in that whenever request is rejected or recalled then email should be sent to the requestor. So here the previous value is approved and new value of status is draft and the email should be sent to requestor.  What I should use here process builder, visual flow or trigger and how to use it

Hi,
There is a custom object in that whenever request is rejected or recalled then email should be sent to the requestor. So here the previous value is approved and new value of status is draft and the email should be sent to requestor.  What I should use here process builder, visual flow or trigger and how to use it