For USPS, they need to use OCR to read the address off the mail. In general, uppercase is more legible and avoids some issues (lowercase L vs uppercase I) Lowe

For USPS, they need to use OCR to read the address off the mail. In general, uppercase is more legible and avoids some issues (lowercase L vs uppercase I) Lowercase is acceptable, but it must meet their guidelines for OCR readability. https://pe.usps.com/text/pub28/28c2_002.htm https://pe.usps.com/text/pub28/28c2_002.htm