Hopefully some of you experts might be able to help me.
Somebody has paid me for a domain name which I own (haven't transferred yet). They said they could only pay me in bitcoin on cryptcarbon.com
The payment is there but is the site genuine?
When I try to make a withdrawal to a Kraken wallet it says I have to send 0.02 bitcoin from the Kraken wallet to verify my address with them before I can make a withdrawal.

Is this a con or are they genuinely just wanting to verify the wallet address?
Please help, many thanks.
Jon