The five processing categories for mailpieces are?

• A. Letters. Flats. Machinable Parcels. Irregular Parcels, and Outside Parcels.
• B. Letters. Parcels. Boxes. Envelopes. Cards.
• C. Postcards. Letters. Packages. Bulk Mail. Oversize.
• D. Standard. Priority. Express. First-Class.

Answer: (A)

Mail processing uses five categories based on size, shape, and whether the piece can be handled by automated sorting equipment. Each category determines the path the mail takes through the sorting system.

Letters are the smallest, most uniform pieces that easily pass through letter-sorting machines. Flats cover larger, but still flat and flexible items that don’t fit as letters. Machinable Parcels are items that are big enough to be parcels but still within the size and shape limits that allow them to be sorted by parcel machinery. Irregular Parcels are parcels with unusual shapes or dimensions that don’t feed well into standard parcel sorters and often require more manual handling. Outside Parcels are the largest or most nonstandard items that fall outside typical machine sorting capabilities and need special processing steps.

This framework is why those five categories are grouped together—they reflect how the mailpiece’s physical characteristics determine how it’s sorted and routed, maximizing efficiency and accuracy in processing. Other options describe service levels or generic container types, which don’t align with the official processing-stream classifications.