USPS employees are dumber and lazier than either UPS or FedEx. And that's saying something!
Parcel post is not tracked and is super slow...it is also SUPER CHEAP...you get what you pay for. USPS PRIORITY beats UPS and FEDEX for both cost and on time delivery. Unfortunately, USPS sucked for so long that it is taking a while to recover and people use UPS and FEDEX out of habit
Parcel Post is what it is. The cheapest way around. It is used by Readers Digest, and various ASSEENONTV crap outlets that say “allow 4-6 weeks for delivery” so they can get bulk rates. Look into Flat Rate Priority boxes. (This lazy, dumbA$$ delivered 6 40lb boxes of antique brick to a restoration project for 11 dollars and change per box, PRIORITY MAIL) with delivery confirmation.)
If you really ship 20K per month, I might be able to save you a bundle. If you are interested, PM me.