I never join any airdrop that requires email because this is the decentralized community. If someone asks me email to send coins or tokens, I reject and stop the conversation right away
This is probably good practice, but in today's day and age I can't see how you can refrain from giving some information up. I have a secondary email that I use for all of these airdrops/forums and that uses protonmail, something I'd highly recommend. Service is good and safe. Beyond that, I don't see much to worry about when giving out this secondary email. Sure people can spam you but that's easy to take care of. Phishing attempts may happen but that's just your own diligence letting you down if you can get scammed by those - never click a link unless you can see exactly where it's going and you have an idea of who it's from.