Life's too short to give a real email address to any random web site that requires registration. One reason is privacy, as they will inevitably sell one's data to a thousand data brokers. Second reason is to avoid having to deal with all the spam, that will again inevitably come. Even if unsubscribed from everything, we've change our policy emails and other nonsense will keep wasting one's time.
I have my own SMTP server that I use for all purposes. I have set up a separate address for each person/service that I use email with. If I receive spam or other unwanted messages, then it is easy to delete that email address, which will cause the SMTP server to return an error message to any client that tries to send messages to that address.
