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; email@example.com and firstname.lastname@example.org are both delivered to email@example.com. 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 firstname.lastname@example.org, 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.