There won't be an easy fix to this. Does the email provider still own that domain? If so, you could send them an email and ask if they'll temporarily give you your email address back (if it's say more than 1BTC that you've lost, I'm sure a company will happily accept $1000 just to give you an email address for a day (depending on how the company functions though of course and the reason they gave up on hosting email address servces to start with.
Are you sure you never backed up your wallet? No external hard drive or flash drive that you had that was small that you though, hey why not put this on here as a spare copy.
Also, does the email have you name in it, ask them if there's anything they can do if you prove your identity. And if someone else owns the account then they'll have an assurance in the fact that your identity is with them so it's less likely you'll scam (unless that identity you send is a false representation which it won't be).
Hi jackg,
thanks for you reply.
I already tried with the new email domain holder, but they refused to do anything...and the mail address does not have my name in it.
I have backups from that time, also with a wallet.dat in it, but it was the "new" one, and not the "old" one that held the payout address that was registered with the mining pool account. No other backups are possbile, because older USB sticks from that era stopped working so I got rid of them. I also swapped my HDDs in 2015 for larger models.
Btw, we are talking here about 0,66 BTC. I am also happy about PMs and would of course share the payout with someone, who gives me a hint that leads to the successful retrieval of the payout...