I've been searching for a mail filtering solution that works with zimbra without any luck at all. I know that zimbra uses sieve to implement the filters specified by users but what I am looking for is a filter that is hidden from the users and will run regardless of the filter settings of the individual users. Maildrop comes closest but it's lack of LMTP support makes it unsuitable for zimbra, unless there's a way to implement it that I don't know of.
I'd appreciate suggestions on how to deal with this. Thanks!