I'm looking to replace an old sendmail server with Zimbra, however I've come across one thing I can't find out how to replicate.

In the old sendmail server there is a virtual user: user@domain which is delivered to alias@domain. That is simple enough. However (on the current sendmail server) when we receive user+{anything}@domain it is processed as if it was sent to user@domain (ie drops the "+{anything}" and processes as if it was user@domain). That I can't work out how to replicate with Zimbra. Is this possible and could you please point me in the right direction or documentation?