Final answer:
OCR systems read text most effectively from a windowed envelope due to its clear window showcasing the address. Padded, airmail, and manila envelopes can present challenges due to their textures and patterns, affecting OCR accuracy.
Step-by-step explanation:
The envelope that is most easily read by an OCR (Optical Character Recognition) system is a windowed envelope. OCR systems are used to convert different types of documents, such as scanned paper documents, PDFs or images captured by a digital camera, into editable and searchable data. Windowed envelopes are designed with a clear plastic or glassine window that allows the enclosed paper's address to be visible. This feature makes it simpler for the OCR system to read the address without interference from the envelope material itself, which can pose issues for OCR accuracy with other types of envelopes.
Padded envelopes, airmail envelopes, and manila envelopes generally have a more complex surface and may introduce textures, patterns, or thicknesses that can disrupt OCR's ability to accurately read text on the enclosed document. A windowed envelope, with its smooth, clear window area, presents the printed text in a way that is more conducive to OCR technology.