Possible Clues:

• Funeral bugle call
• Call for evening collection
• There'll be no more mail after this - you'll get it on the blower
• No more letters of late, by the sound of it
• Final bugle call
• Military bugle call sounded at sunset
• Late dispatch sounded at late dispatch?
• Military bugle call at sunset and funerals
• No more mail on the blower
• Final job and call for retirement