Answer: ENCL
ENCL is a crossword puzzle answer that we have spotted 58 times.
    - Postal letters?
 
    - A check, one might hope: Abbr.
 
    - Abbr. on a business letter
 
    - Business letter abbr.
 
    - S.A.S.E., e.g.
 
    - Abbr. at the bottom of a business letter
 
    - Letter accompanier: Abbr.
 
    - Bottom-of-letter abbr.
 
    - Check inside?: Abbr.
 
    - Letter abbr.
 
    - Letter-bottom letters
 
    - SASE, for example
 
    - SASE, for one
 
    - SASE, e.g.
 
    - Pkg. insert, e.g.
 
    - Unsolicited MS., perhaps
 
    - Cover letter accompanier: Abbr.
 
    - Lesotho, to South Africa
 
    - Something sent with a ltr.
 
    - Ltr. insert
 
    - Letter-bottom abbr.
 
    - It's inside: Abbr.
 
    - Env. contents
 
    - It's inside an env.
 
    - It's in an env.
 
    - Letter add-on (Abbr.)
 
    - Abbr. on a business letter, perhaps
 
    - Like an SASE, often
 
    - Abbr. on an envelope
 
    - Env. in an env., e.g.
 
    - Check sent with a ltr., e.g.
 
    - Env. stuffer
 
    - Abbr. at the bottom of a letter
 
    - Return envelope, e.g.: Abbr.
 
    - Env. thickener
 
    - Inside this env.
 
    - Abbr. on the bottom of a business letter
 
    - Something in an env.
 
    - Inside, for short
 
    - Check within, say?: Abbr.
 
    - SASE, often
 
    - Env. stuffing
 
    - S.A.S.E., e.g.: Abbr.
 
    - Letter accompanier (abbr.)
 
    - Env. within an env., perhaps
 
    - Something besides the letter: Abbr.
 
    - Bus. letter abbr.
 
    - Letter letters
 
    - Ltr.-bottom letters
 
    - Chem. ending
 
    - Like many cks.
 
    - SASE, say
 
    - Acct. statement, at times
 
    - Extra item in an envelope: Abbr.
 
    - Env. fattener
 
    - Anything in an env.
 
    - Something in addition to the letter: Abbr.
 
    - Mail insert: Abbr.