By way of background, I always ship swap books in bubble mailers. When shipping a paperback that PBS suggests shipping via first-class, I use the "large envelope" rate based on weight measured by a digital scale. When I take such a book to the local P.O., I'm routinely told that I owe additional postage money; the explanation is that unless the envelope is completely flat (which no book will be) the first-class package rate applies. However, if I put the same book in my rural mailbox, where it's picked up by the carrier and taken to the area processing center, it goes through with no additional postage required. Which USPS agency is correct here? I don't want to risk having books delayed by return for additional postage, but also don't want to pay more than necessary. Any help will be welcome and appreciated; thanks-

Ruth

A large envelope is a flat piece (less than 1/4 inch thick, with no "bumps"). It is just like a first class letter, but overzixe.

A Book in a bubble mailer is a First Class Parcel: 1/4 inch thick or uneven thickness.

Since the large envelope can go through the sorting machines, it is less than a parcel.

wc

Even if your book is less than 1/4" thick, it can't be a "large envelope" unless it bends at least one inch in each direction.

There's a thread in the Questions about PBS forum from someone who keeps receiving packages with postage due. The amount of postage due is the difference between the first class large envelope and parcel rates. So you probably aren't the only one doing this, but it's still wrong, and the requestor does have the right to refuse any package that arrives postage due if she wants to.

A lot of times you'll be able to get away with it, but not always. You could get books returned to you, or they could arrive postage due. Your local P.O. is correct. 

Thanks, everyone; that's what I needed to know. I'd hope that anyone receiving a book from me with postage due would let me know so I can reimburse them; but clearly that's not always the case. I'll certainly use the parcel rate from now on, and thanks again-

Ruth

Hi, I always ship my books through Paypal and yesterday when I went inside to pickup a box, the postal worker told me my flat first class manilla envelope cannot be used with  that confirmation number. You have to buy theirs which costs .70 cents. She said they have just started enforcing it since the economy has gone down. The envelope will arrive postage due. I brought it home and added a piece of styrofoam and went back and it was okay since it was over 1" thick.