I have one email for all my bounty and airdrops and if I received unusual offers I just click the spam email link and next time it will land in the spam folders and about KYC I stopped doing KYC from some bounty and if they require bounty I have one of my team, willing just a share of the token.
I generally recommend having a different email for each case so that it is as easy as possible to sort messages. not only spam emails but all incoming messages