Any decent email hosting service should allow you some form of aliasing (whether it's plus addressing or actual aliases). Ideally there should be no "default" address associated @your.domain, it should be all aliases. Preferably with wildcards so you can make them up on the fly when subscribing to a random website, without having to go into the admin settings. And naturally they should also offer wildcard sending (being able to send from anything@your.domain – this is supported by most decent email clients).

Bottom line, as long as it's your own domain and you don't abuse things like receiving/sending limits, attachment size, total storage size etc. you should be able to do whatever you want with your addresses and mailboxes.