Whoops. Looks like I totally misread that OP. Yeah... aliases is what I was thinking about as well.

Although, separate email adresses in conjunction with a catch-all are better. After all, with an alias, you can just cut the recipient's address off just before the + which isn't that big a hurdle to spammers...

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.