Ideally, of course, you want to avoid unsolicited emails entirely, but in the absence of an ideal, using a unique address per site is probably your best defense against being added to an email lists without your permission and for preventing your inbox from being flooded with spam. Your best bet is to use a throwaway email. Set up an email that you don't mind getting spammed, and use it whenever necessary. This way, you'll have a unique email address per site, and your main inbox will remain relatively spam-free. This is especially important if you're signing up for sites that are likely to send out unsolicited emails; it's unlikely that they'll care whether or not your email address is valid.
I'd see this as a very common problem for everyone. A number of emails even going to receive almost every day and possibly some of them are on the purpose to scam us. And if we are too careless to handle this, this may lead to something terrible happening to us. That is why I don't save important documents on my computer, bank accounts, and passwords as these are the usual target for these scammers. Now, as technology has been improving, the more we got prone to hacking incidents and many have become a victim of this.