Global duplicate filtering via Sieve

Hi everybody,

I have the following problem:

Our mail users are receiving mails from externally defined mail forwardings and lists which sometimes leads to duplicate messages. As far as I understand, a single user can use the Sieve duplicate extension for filtering out such duplicate messages.

Would it be feasible to add a script with sieve_before that does this for all users?

Do scripts that run from sieve_before store persistent data also on a per-user basis, i.e. in the user's home dir?

Thanks for your help!

Best regards

Hanno