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The nonmachinable surcharge is extra postage for letter-size mail that can't run through automated sorting machines: square envelopes, rigid or lumpy contents, clasps, and wax seals. If your envelope can't bend or has anything bulky inside, it gets pulled for hand sorting, and you pay for that. LetterAgent letters are plain printed pages, so this never applies.
| Trigger | Why machines reject it |
|---|---|
| Square envelopes | Machines orient mail by its long edge; a square has no long edge, so every square envelope is hand sorted |
| Rigid contents (keys, coins, thick cards) | Sorting rollers bend letters slightly as they move; rigid pieces jam or snap |
| Clasps, string-and-button closures, or bulky knots | They catch on belts and rollers and tear the envelope open |
| Wax seals | Raised lumps of wax crack, smear, or jam high-speed equipment |
| Anything too thick or too stiff to flex | Letters must bend around the machine path; stiff mail cannot |
Automated sorting orients each envelope by finding its longest side and feeding it in a fixed direction. A square envelope has no longest side, so the machine cannot orient it, and it gets kicked out for manual handling every single time. There is no way to make a square envelope machinable. If you love the look of a square invitation, budget the surcharge or step up to a larger rectangular envelope.
Real wax seals are the classic wedding-invitation trap. The raised blob of wax does not survive high-speed rollers: it can crack, smear across neighboring mail, or jam the machine, which is exactly what the surcharge pays for. If the seal matters to you, you have two good options: use a flat adhesive seal sticker that looks like wax but sits flush, or put the sealed invitation inside a slightly larger outer envelope so the machinery only ever touches plain paper.
Stick to a standard rectangular envelope with flat paper contents that bend. That combination sails through the machines with no surcharge. When something in the envelope cannot bend, do not try to sneak it through as a regular letter: pay the surcharge (or the large-envelope rate for bigger pieces) and it will be handled by hand. Trying to dodge it usually ends with the envelope returned for more postage or arriving torn.
Canada Post handles it through its size and shape rules rather than a line item called nonmachinable. Square, rigid, or oddly shaped pieces fall into higher-priced categories, so the same principle applies: flat and rectangular is cheapest, and anything unusual costs more.
Ready to mail it? Send your letter with LetterAgent - describe it to your AI assistant, approve the exact quoted price, and it's printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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