Most aliases require adding explicitly. The primary feature of the catchall address is that it is a blacklist rather than whitelist for aliases. Gmail style +

Most aliases require adding explicitly. The primary feature of the catchall address is that it is a blacklist rather than whitelist for aliases. Gmail style + aliases (which don't require explicit adding) are almost as good, but can be easily and silently stripped and generally notify the receiver that a filtering situation is happening on the other end.