Related Clues:

• Letter-bottom abbr.
• See 46 Across
• Letter-bottom letters
• Env. inside an env., e.g.
• Spam, say
• It's in an env.
• Use the USPS
• Something sent with a ltr.
• Vacationer's accumulation, perhaps
• Env. attachment
• Check, perhaps: Abbr.
• Letters in a box
• Unsolicited MS., perhaps
• E or G follower
• Bills, circulars, etc.