Often, there's an overflow of "bubble" envelopes as well.
Most of the non-postal boxes and bubble envelopes are from items ordered on-line, Amazon is our prime supplier of CDs, batteries, and some over-the-counter lotions that are not available locally. The Amazon prime membership ($79 annual fee) that's shared between Grenville and myself gives "free" 2-day shipping and it's been tax-free as well. BUT, as of Sept. 1, Amazon is collecting sales tax on orders of new items sent to our VA home. But, that doesn't seem true for used CDs, which I order often (and receive in — that's right, a bubble mailer).
We don't save EVERY box, but some smaller or "odd" sized ones are broken down and stored in a back closet.True, the post office gives some boxes free when using flat rate priority mailing, but sometimes it's difficult to find just the "right" size to avoid paying more for a larger box. Some of our re-used boxes have traveled cross-country. Today, one came from California and was re-purposed for mailing something to Florida.
Bubble envelopes in good condition are always saved. These come in handy for mailing books to friends. Only problem is that mailing a book (even at media rates) always costs more than its original thrift store cost.
But, at least the re-used envelope didn't cost much.