With iOS 15 and the Hide My Email feature exclusive to iCloud+ subscribers, you can create unique, random email addresses that forward to your personal inbox whenever you want to keep your personal email address private. In iOS 15.2, which is in beta right now, you can use Hide My Email directly from the Mail app.
When you use Hide My Email, all the emails sent to the random Apple-created email address are forwarded to you so you can respond if needed, but the person on the receiving end does not see your real email address.