by return

by return (of post)

Through prompt mail correspondence back to the sender. Primarily heard in UK. Please indicate your interest in this offer by return of post.
See also: by, return
Farlex Dictionary of Idioms.

by reˈturn (of ˈpost)

(British English) using the next available post; as soon as possible: Please reply by return of post.
See also: by, return
Farlex Partner Idioms Dictionary
See also:
  • by return (of post)
  • by return mail and by return post
  • mail
  • by return mail
  • by return post
  • is that right
  • is that so
  • Is that so?
  • Is that a fact?
  • Is that what they're calling it these days?