eBay Standard Envelopes being rejected by USPS

[lakehousegoodies]

I have mailed many postcards and coins with the eBay standard envelope option with no issue. The post office just returned one of my envelopes and I was told by the Supervisor at the local USPS office that even though we used to be able to use any envelope as long as it met the measurement and weight requirements, they will no longer be accepted.  Anyone else heard of this change? 

[pnwdiecast]

That's what I do - I either drop them off in our locked community outgoing mailbox, or at one of those privately owned "U Ship" places where USPS picks up from. So far never had an issue.

Also in response to @onefootflipper I use plain white 5x7 envelopes which don't seem to attract unwanted attention. I also use brown kraft 5x7 envelopes for certain orders and those go through without an issue.

For coins, I pack each individual coin in a 2x2 plastic baggie, wrap in a piece of paper, and tape to the inside of the envelope.