@byamrcn
Most of the "mailers" are too stiff to rapidly pass through the high speed (32,000 envelopes an hour!) USPS roller system -- the envelopes need to bend nearly in half to easily pass through the system.
The eBay Standard Envelope (ESE) is intended for individual items valued at $20.00 or less, or multiple items valued at no more than $50.00 total -- so that may limit which cards you may choose to ship using the ESE. And the total weight needs to be 3 ounces or less.
Similar to other responses which you have received, I also use a #6 envelope, into which I insert two pieces of carton material from either cereal boxes or 12-packs of soda (the inserts should fit snugly inside at all sides). Between the two inserts, I place a trading card (in a penny sleeve -- nothing thicker & nothing less flexible) or a stamp (in a simple glassine envelope). Print the ESE label and trim to fit the #6 envelope -- seal with tape on all sides -- and mail in the "Metered Mail" slot in the post office lobby.
IMPORTANT NOTE!!! Do NOT hand the ESE to the USPS counter workers, or to your USPS delivery drivers -- the ESE is business metered mail, and can NOT be scanned by the USPS employees -- the ESE is machine-scanned at the USPS Distribution Centers (and NOT at your local post office). If you hand the ESE to a USPS employee, they will probably demand additional postage.
It is probably also NOT a good idea to mail the ESEs from your own home mail box, or the USPS "blue" boxes," as your initial "Accepted" scan from USPS may be delayed, or never get scanned at all -- and you ABSOLUTELY need that initial "Accepted" scan to be covered by eBay insurance for any losses. (Please note: this is eBay insurance, and NOT insurance through USPS.)
Your initial scan may be delayed by a day or two, since that scan happens at the next USPS Distribution Center, which is often in another city, or even another county. And if you mail the ESE on a Friday, it may not receive the initial "Accepted" scan until the following Monday -- or even later, if a three-day USPS holiday is involved.
In addition, the final "Delivered" scan ONLY means that the ESE has been received at the post office matching the ZIP Code on the buyer's address -- the ESE will probably be delivered a day or so later, unless the "Delivered" scan was made on a Friday -- and then the residential delivery may not be made until the following Monday or Tuesday -- unless a three-day USPS holiday intervenes again.
Yeah, I know -- it all sounds really complicated, doesn't it? And not as easy as just sticking a First Class stamp on an envelope, and sending it off.
But quite a few of us have been using the ESE for years, and we have learned the hard way about what works -- and what doesn't!
So try out a few ESEs on your own -- and eventually you'll get the hang of it, too.
Good luck!
