I have exim set up to accept all mail to my domain that starts with a particular prefix. So I sign up to websites as myprefix-sitename@mydomain.com. Setting it

I have exim set up to accept all mail to my domain that starts with a particular prefix. So I sign up to websites as myprefix-sitename@mydomain.com. Setting it up was a bit of a fiddle because I suck at exim, but it's no ongoing hassle.