Buying domains on eBay are very risky as I said, because if the seller decides not to transfer the domain PayPal will not refund you. PayPal has a policy against refunds for intangible goods. They offer no buyer protection for goods that can show no proof of deliver.
If you are going to use eBay use only to sell domains, not buy. As you see below PayPal offer no buyer protection for Intangible goods. So once again PayPal/eBay is safe for selling, but not buying.
Items are eligible unless they are excluded below:
Real estate, motor vehicles, capital equipment, travel tickets, and events tickets
Intangible items
Services
Items purchased using PayPal Payments Pro or Virtual Terminal
You may not file a dispute for a Personal Payment
Depending on your credit card company, you may be able to do a chargeback, if you funded the payment by CC. This is the buyer protection you need.
Now if you're on the seller end and the buyer who has no Paypal Buyer Protection but DOES have credit card protection files a CB for non-receipt of the item, you the seller without Paypal Seller Protection will lose the claim.
Also, if the buyer is not an authorized credit card user but has stolen someone else's credit card or Paypal account then the CC company will issue a chargeback and Paypal won't cover it. OTOH, if it is a tangible item and you can prove it was sent to the buyer's city and state or city and country or zip/postal code.
One option is to email the auth code and also snail mail it with delivery confirmation (unless buyer refuses delivery). Use a packing peanut to make envelope at least 3/4" thick as FCM requires this (Priority doesn't, IIRC) for DC to be scanned.
PayPal User Agreement
11.3(b) Item Not Received Additional Requirements: ... You must provide Proof of Delivery as described below in Section 11.4.
11.3(c) Unauthorized Transactions Additional Requirements: ... You must provide Proof of Shipment or Proof of Delivery.
11.4 Proof of Shipment, Proof of Delivery and Signature Confirmation Requirements.
"Proof of Shipment" is online or physical documentation from a shipping company that includes all of the following:
The date the item is shipped.
The recipient’s address matches the shipping address provided on the Transaction Details Page.
The recipient’s address, showing at least the city & state, or city & country, or zip/postal code (or international equivalent).
"Proof of Delivery" is online documentation from a shipping company that includes all of the following:
The item’s status as delivered.
The date the item is delivered.
The recipient address is the same as in the shipping address section on the Transaction Details Page.
The recipient's address, showing at least the city & state, or city & country, or zip/postal code (or international equivalent).
Signature Confirmation as described below if the full amount of the payment including shipping and taxes is $250 USD or more or its foreign currency equivalent provided below:
[Click on link above to see the table of foreign currency equivalents]
"Signature Confirmation" is online documentation that can be viewed at the shipping company’s website and indicates that the item was signed for on delivery.