But I knew people that lost "precious" cards in the mail. I don't remember in which direction though.
If you are into multiple awards (e.g. 5BWAZ
and DXCC) it doesn't matter.
That is why I have never mailed in a card for award credit. I have always found another way, no matter how far the drive.
If the ARRL finally decides to audit my most recent card submission, I suppose I would have to mail that set to Newington. If I did, I probably would send them via UPS, FedEx, or even USPS Express Mail. They could still get lost, but the odds go way, way up done that way. They scan the package not just once, but all along the way.
Regular mail is better than we think, but not foolproof. Your card checker mails in your submission, of course. Mine takes extra steps. He told me he takes all submissions to the main post office, which eliminates some of the handling, at least on "our" end of it. Smart man.