Recruitment Rejection emails/notifications

In our Standard Candidate Selection process we have 3 phases (New, Screening, Interview and Selection). In each of these phases we have a step called Rejected by Employers, which is an email notification when a candidate was rejected. We would like to find out how we can check what/when and to who those notifications/emails were sent. We don't seem to be able to allocate them in the system. Any advise will be appreciated. Thank you