Not worth voluntarily putting myself on their mass email list in addition to them selling my email. Those companies offering those giveaways actually make money selling their email lists. The giveaways cost them nothing.
That's how I found out about it, they emailed me! I try to avoid giving out my email as well, but I was already on their list from prior orders.
If you plan on entering giveaway’s like that, just use a separate email that doesn’t matter. If you don’t have one, you can make a free gmail account in 5 minutes lol. Try not to give out your personal email to a bunch of companies just as safety against hackers and such.
My email is connected to nothing of importance. No bank accounts, no credit cards. If they want to hack me they'll have to come visit me in person out in the northern woods where I live!