[dau]

I am using my own domain with Fastmail for years and can set as many aliases as I want. So I use an alias for every account I have that requires a mail address to sign up. Occasionally I get a spam on one of these addresses and immediately know that the associated service/website had a potential data breach and the address and all my personal data was likely hacked/sold/leaked from there.

[Vaslo]

I don't know why I didn't think of this.