Related Clues:

• Letters on many business letters
• Abbr. under an address
• Ltrs. in a letter
• Ref. wd.
• Abbr. on a business envelope
• Bottom-of-env. header
• It's added to an env.
• Env. add-in
• "Look inside" abbr.
• Stamped return env., for example
• Placed inside: abbr.
• Routing abbr.
• Something inside an env.
• Bus. letter abbr.
• Abbr. before a name in a memo