Related Clues:

• Abbr. on a cover letter
• Return envelope, e.g.: Abbr.
• It's inside an env.
• 25 Across, for one: Abbr.
• SASE, e.g
• Envelope abbr
• Check included with a ltr., e.g
• Bus. letter notation
• Inside this env
• S.A.S.E., for one
• Env. addition
• It's inside an env
• End-of-letter abbr
• Business letter abbr
• Insert of a sort: Abbr