Add a delete File behavior to the page.
For the Folder, use the same settings you used in the Upload File Behavior.
For the File Name, click the lightning bolt and select the Server File Name binding from the Uploaded Files Binding group.
after the delete file behavior is added to the page, you may need to rearrange the code order in code view to make sure that the code for the upload file behavior is first, the email behavior code is second and the delete file code is last.