LetterAgent
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Home > Guides > Red Ink on Envelopes
You can, but don't. Automated mail equipment has trouble with red ink, orange ink, and pencil, and those letters are more likely to be slowed down or missorted. Black or blue ink on a white or light envelope is the combination the machines read best. Pencil adds a second problem: it smudges and fades in sorting machinery, so even a well-written address can become unreadable in transit.
Postal scanners often read mail under red light, and red and orange inks reflect that light right back: to the camera, the address can look blank. Pale inks like light green and pink fail for the same reason, just less dramatically. Black ink absorbs the light and gives the crisp contrast the software needs. This isn't a preference: it's physics, and it's why postal guidelines in both the US and Canada call for dark ink on a light background.
Two things. First, graphite is low contrast: a pencil address is gray on white, and scanners want black on white. Second, pencil smudges. Mail gets tumbled, squeezed, and rubbed by machinery on its way across the country, and a pencil address can fade into illegibility before it ever reaches a reading station. Pencil also erases, which matters if the letter is delayed and handled more than usual. For anything you want delivered, pencil is the wrong tool.
| Pen | Verdict |
|---|---|
| Black ballpoint | Best choice: dark, permanent, and consistent |
| Blue ballpoint | Nearly as good and widely accepted |
| Black felt-tip or marker | Fine on plain envelopes if it doesn't bleed through |
| Red, green, or purple ink | Avoid: poor contrast under scanner light |
| Pencil | Avoid: smudges, fades, and erases |
| Gel pens on glossy envelopes | Risky: they can smear before the ink sets |
Two more placement tips: keep the bottom edge and right side of the envelope clear so the post office has room to print its routing barcode, and write the address parallel to the longest edge. Decorations are fine elsewhere on the envelope: just keep them away from the address block.
The same contrast rule applies to the paper. A dark red, navy, or black envelope gives the scanner nothing to work with, no matter what ink you use. Patterned or textured papers are nearly as bad: the background noise confuses the reader. If you love colored stationery, use it for the letter inside and put it in a plain white or cream envelope. Dark envelope plus white address label is the other safe combination: the label restores the contrast the scanner needs.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is 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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