how can I disable/restrict APPEND, but allow COPY to ?

[Ana Ana]

I think about using Cyrus IMAP to share a mailing list archive.


   The archive will be stored in some public folders , and  every user
should have his own personal folders. These folders will allow every
user to make a personal selection and classification of the messages
in the public archive, by grouping them into folders using some
personal criteria ( like topic, sender, interesting/boring and so on
). Users will be able to share their selections among them ( with ACLs
),  to use sieve to filter ( new ) mailing list messages.

  The problem is that I want to prevent users  appending ( uploading
from  their MUA ) messages  to the mailboxes, but in the same time
they should be able to copy/move messages from one folder to another. 
( I don't like  500 hundred people which I know only from the net 
using my server and bandwidth to share photos,  cracks and  music. I
also don't like to have to deal with fake list-messages, with viruses
and trojans.)

  Can this be done? How?


 Thank you.
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