[joobus]

It's not exactly a catchall; it's per user, and you can also set up rules to route to different folders based on receiving address. If there are 2 users 'joe' and 'bob' on the domain 'foo.com', joe can use any '* @joe.foo.com' address and bob can use any '* @bob.foo.com' address. Fastmail pricing is per user.

[brlewis]

Side note: Both joe and bob would have trouble proving in court that their addresses were sold, not guessed.

[labawi]

Individually, it doesn't seem convincing, but if you find multiple instances (individuals), in their own different styles, and all the addresses are in the same mailing list... I think it can have significant weight. Alternative would be what? Someone framing the service provider? Or joe and bob and maybe others staging it? Possible, but frankly, not very likely. I think the service provider would have at least have some explaining to do.

[ehPReth]

what if each local part was something long & random?