mail split for mail alias?

We have an alias which everyone gets mail at, some of the information is
worth archiving. So what we want to do is to build a searchable index of
all the messages split up by user and then number so it looks something
like


archive
        user1
                1       <--- individual message
                2
                3
                4
                5
        user2
                1
                2
                3
                4
                5

Basically, we want to periodically run a unix spool style file through
this filter to generate this. Can someone tell me of a quick recipie that
can do this? It would be much appreciated. Thanks.


--Jauder