It's unlikely that FT is selling our emails. More likely, the spammers are using a spider to collect all the emails it can from bulletin boards all over the web - it is relatively easy for a software program to do that - and then that spider-generated list is rapidly sold.

Never reply to unsolicited spam - even to unsubscribe - that will confirm your email is a working address - lists of confirmed email addresses cost a lot more and get distributed to other spammers quickly.