Destructoid has published a guide for the game Cat Mail Co., explaining the different "package constraints" players must identify and store correctly to avoid destroying deliveries. As players progress beyond the basic tutorial stage, parcels arrive with special requirements that can only be identified through clues in the recipient's description, making correct handling increasingly important to avoid losing packages.

The guide breaks down each constraint type and its storage rule, using recipient dialogue as detection clues.

– Weight: heavy boxes needing six weight stickers plus a special heavy sticker, stored at the bottom so they don't crush other items
– Fragile: delicate boxes that must be placed on top of a shelf with nothing stacked above them
– Cold: perishable or temperature-sensitive items (e.g. ice cream, catnip seeds, fish) that must go in the cooler room
– Warm: items needing heat preservation (e.g. dragon scales) that must go in the heated room
– Dark: light-sensitive items (e.g. photographic film, midnight spores) requiring the dark room, unlocked by clearing the cooler room's parcel pile
– Light: items needing brightness (e.g. sunflowers) requiring the Light Room, unlocked by clearing the Heating Room's parcel pile
– Partner/Love/Heart: paired packages identified under a lamp by a glowing heart, connected to a second parcel via light beams and stored together