When I sell to someone as a private individual they can email a copy of the FFL or not, as I understand it the ATF discourages that. So I just ask for the first three and last five digits of their FFL number and run that through the ATF EZ-Check website to verify it is valid and current, then ship to the address posted there.

I also state very clearly in my ads that their FFL must accept shipment from a private individual.

Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!