I just sent some BTC to Bitcoin Fog. Used the onion-link from bitcoinfog.com. The coins arrived in my deposit. Now I want to withdrawl them to an electrum wallet receive address and enter it. Then I need to confirm the withdrawal, but the address after "To: <address>" is different to the one I entered. Only about the first 3 characters match. What am I doing wrong?
Check near the bottom of the /r/DarkNetMarkets Superlist for tumbler sites and warnings:
https://www.reddit.com/r/DarkNetMarkets/wiki/superlist
What is the exact onion URL you used? Does it match the one on the Superlist?
Since bitcoinfog.com is an unencrypted clearnet site, it's possible that a bad Tor exit node substituted a different onion address and sent you to a scam site. This tactic was recently used against the darknet email service SIGAINT:
https://www.deepdotweb.com/2015/04/26/70-malicious-tor-exit-nodes-exposed-by-siganit-org/