There are some aspects of the writing business that the march of time has marched right on past, and I don’t miss them even a little bit.
The SASE, or Stamped And Self-addressed Envelope, for manuscript submissions, is one of them — because when you had only one good typescript of a story or a novel, you were going to want it back. So first you had to get an envelope, or a cardboard box, that would fit your manuscript; and then you had to get another envelope or cardboard box that would fit into the first one along with the manuscript; and after that you had to get the post office to weigh first the manuscript and both envelopes (or boxes) and then the manuscript and just one envelope (or box); and before you could put the manuscript in the mail you had to double-check and make sure that the correct address and postage for the outer box had actually gone onto the outer box, and the correct address and postage for the inner box had actually gone onto the inner box . . . and when the manuscript finally got rejected and came back to you, you had to start the entire process all over again.
It’s a whole lot easier just to do the whole thing by e-mail; or if you’re dealing with hard copy, to slip in an ordinary self-addressed business envelope with a single first-class stamp on it, and put in your cover letter the magic words, “Please consider this a disposable manuscript.”