What is the difference between USPS parcel post and USPS priority mail?
USPS parcel post is a ground surface offered by the USPS, and is
estimated to take from 2 - 9 days, or up to 14 postal business
days. Priority mail takes priority over parcel post and first class
mail, is usually sent by air, and can arrive in 2-3 days, with a
maximum of 5 days. parcel post accepts larger boxes/packages, while
priority mail does not. Parcel post is a different service from
bulk mailing, which is used by businesses who mail out large
amounts of mail at regular intervals.