maildirproc is a program that processes one or several existing mail boxes in the maildir format. It is primarily focused on mail sorting — i.e., moving, copying, forwarding and deleting mail according to a set of rules. It can be seen as an alternative to procmail, but instead of being a delivery agent (which wants to be part of the delivery chain), maildirproc only processes already delivered mail. And that's a feature, not a bug.
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