One feature I really like in gmail is the "plus sign" (+) in a username so that you can specify fake addresses for using online:

1 Awesome Gmail tip You Don’t Know about. Seriously. | MakeUseOf.com

How would one configure Zimbra to handle that? I'd love to tell my users they can do username+domain@ourdomain.com for all the sites that they put their email address on.

--Ajay