Logbook Of The World
This is my preferred QSL confirmation method, especially with the costs of cards and postage nowadays.
I will NOT entertain any requests for payment for you to confirm our contact via LOTW, if I want to donate to your expedition, I will, but I will not be held “hostage” to getting a DXCC with a PayPal payment. If this is your requirement, the contact will remain unconfirmed, I am not a DXCC or award chaser.
Info about LOTW on Wikipedia: https://en.wikipedia.org/wiki/Logbook_of_The_World
Official ARRL LOTW site: https://www.arrl.org/logbook-of-the-world
For those who need to learn about LOTW, start here: