Address extensions ( aren't working for me. This is a problem since I have been using a whole bunch of these before I cut over some of my MX records.

My postfix has the following:
# ADDRESS EXTENSIONS (e.g., user+foo)
# The recipient_delimiter parameter specifies the separator between
# user names and address extensions (user+foo). See canonical(5),
# local(8), relocated(5) and virtual(5) for the effects this has on
# aliases, canonical, virtual, relocated and .forward file lookups.
# Basically, the software tries user+foo and .forward+foo before
# trying user and .forward.
recipient_delimiter = +

But I imagine all of the zimbra accounts are virtual, so I'm wondering if there is something I can configure inside zimbra to allow this.