# Really weird USPS mailing question **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2026, 11:22pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781 "2026-01-17T23:22:27Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [January 17, 2026, 11:22pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/1 "2026-01-17T23:22:27Z")
I’ve posted before about mailing folded self-mailers. In addition to the size and weight requirements for standard mail there is also a limitation on stiffness: the item has to be flexible enough to feed through the machines that process mail, so you could not for instance mail a rigid piece of flat plastic (without paying a special handling surcharge) even if it met all the other guidelines. So here’s a weird question that I haven’t found an answer to: what’s the _flimsiest_ a piece of mail can be? If for example you wanted to an a-hole and contrive a letter and envelope out of the most gossamer paper you could. What would the USPS reject, and what would be the dividing line? ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [January 17, 2026, 11:56pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/2 "2026-01-17T23:56:37Z")
I’m not sure there would be a rejection. Perhaps, instead, the addressee would receive a plastic bag containing the salvaged shreds of the article and a note indicating the article had been damaged by processing. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [January 18, 2026, 12:16am UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/3 "2026-01-18T00:16:42Z")
[USPS mail standards](https://pe.usps.com/text/dmm300/101.htm) says minimum thickness is .007 inch. Anything thinner is subject to a non-machinable surcharge. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [January 18, 2026, 12:36am UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/4 "2026-01-18T00:36:50Z")
Okay, although I wasn’t planning to put this to the test, I don’t have any thousandth-inch calipers. I’m now curious to look up the thickness of standard grades of paper. **ETA:** standard letter/printer/copier paper is about .004, so two thicknesses of that would be fine. ---
**Author:** ![Misnomer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/misnomer/32/14897_2.png) [@Misnomer](https://boards.straightdope.com/u/Misnomer)\ **Post date:** [January 18, 2026, 12:52am UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/5 "2026-01-18T00:52:41Z")
never mind 🙂 ---
**Author:** ![aruvqan\_myers](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@aruvqan\_myers](https://boards.straightdope.com/u/aruvqan_myers)\ **Post date:** [January 19, 2026, 5:45pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/6 "2026-01-19T17:45:11Z")
have you measured a classic old school air mail onionskin paper? do they still make it? ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [January 19, 2026, 8:41pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/7 "2026-01-19T20:41:52Z")
Sources online claim it was about 46 microns, or 0.0018 inches. So an envelope containing one folded sheet would total 0.0072 inches, about the limit. ---
**Author:** ![aruvqan\_myers](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@aruvqan\_myers](https://boards.straightdope.com/u/aruvqan_myers)\ **Post date:** [January 20, 2026, 4:10pm UTC](https://boards.straightdope.com/t/really-weird-usps-mailing-question/1026781/8 "2026-01-20T16:10:39Z")
I have [somewhere] a few old letters stuffed in the back of my grandfathers desk and the paper is named well - it has that funky thin crinkly onionskin texture. I actually sort of like the texture =)