This is what's wrong with the average ebay buyer

[steve B]

Originally Posted by tschock

I don't think that is true. I've mailed literally hundreds of envelopes with a card (or 2 or 3) in top loaders inside a PWE. I tape the holder to a folded sheet of paper inside the envelope. I also put a piece of packaging tape, wrapped around both ends of the top of the envelope, to avoid the envelope flap catching in the machine. All for a single forever stamp. I've never had anyone come back to me and say they were charged for additional postage (but I deal with great traders so who knows what they aren't telling me ). I've also not had envelopes get destroyed, or if so, no more so than padded envelopes.

That doesn't mean I should NOT do this though. Just that they do seem to be flexible enough to go through when packaged appropriately.

To follow on to another point you made. If you don't like what an PO employee is telling you, ask a different one. They might even tell you how to send a small box of cards using a flat rate envelope.

I went looking for the page, and it looks like they removed the requirements on flexibility.
The piece I had was a photo mailer, about 6x9, with a print and two cardboard stiffeners. It was not at all flexible. The old rule for flats (Now large envelopes) required something like more than 1/4 inch of droop when it was held by one end over hanging a countertop.
For letters it was a certain radius it had to go around in the machine. I always sent cards in either a toploader or sleeved and between two pieces of cardboard. And yes, small lots up to about 400 cards went in small flat rate boxes. (And later when they got expensive, a small flat rate box inside a flat rate envelope. Doable with the smallest flat rate box )

That particular bit of mail I did discuss with a clerk first, who basically said my printouts of the appropriate page from the Domestic Mail Manual (The post offices rule book) didn't matter.
The guy I ended up talking to was the postmaster for the entire city, so not much room to ask to see someone else.
He had his own printout of a different section.
Mine was the standards for what was and wasn't a package, his was for what made a first class package qualify for delivery confirmation.

Ebays click and ship system at the time automatically added DC to everything, even if it didn't qualify.

I shipped enough odd stuff that I knew the rules pretty well. But those rules have lots of room for interpretation. Like how I used to send larger lots of cards media mail since it allowed "unbound printed matter" After a couple years the main office opened one and told me I couldn't do that anymore. My argument that cards qualified as educational materials was not agreed with...