Related Clues:

• Encl. with a submission
• Letter carrier?: Abbr.
• Post delivery: Abbr.
• Part of SASE
• Part of SASE (Abbr.)
• It may have a window: Abbr.
• It may get stuffed: Abbr.
• P.O. item
• Ltr. carrier
• PO delivery
• Ltr. holder
• Letter container: Abbr.
• Mailer, briefly
• Terminate
• Stamp's place: Abbr.