Multiple addresses for one user?
Gmail (and I think some other mail providers) allow users to receive email at multiple addresses using the plus sign; firstname.lastname@example.org and email@example.com are both delivered to firstname.lastname@example.org. The suffixes allow for easy sorting, and better yet, for some degree of spam prevention or tracking (if you're signing up at a dodgy site, use email@example.com, and then if you start getting lots of spam, just filter that address into junk).
Does Zimbra offer anything like that? I looked through the docs, but since I'm unclear on what that's actually called, it's a little tough to search for.