I run my own domain and the mail server I use does that for me (smartermail). If you don't control your domain there must be third party services. I googled "free email alias", most results seem to be for temporary aliases, but there must be a service for permanent aliases. It's something major providers like gmail should provide.

For some websites, you can put a "+" sign and whatever you want after your gmail username. For example: [email protected], and you will receive mails at [email protected]. Unfortunelately, this doesn't work with websites that have aggressive regexp checking on email fields.

I don't see the benefit of using [email protected] if the point is to obscure your email address

Not everyone realises that'+' is a valid character in an email address, at least not when I tried this several years ago.

If you don't want bots to try email+password from a leak on a bunch of websites, it's good enough, but I agree on the fact that it won't hide your identity.

Plus it leaks your underlying email address so it offers very limited protection. Also you can't delete the alias to stop any future spam/phishing.

I think with gmail it's possible to filter based on which alias it was sent to.

I use 33mail