From: Colin Campbell (sgcccdccitec.qld.gov.au)
Date: Fri May 02 2003 - 00:18:53 CDT

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Hi,

On Thu, 1 May 2003 12:21:12 -0400 (EDT)
Victor.Duchovnimorganstanley.com wrote:

> If anything, I would propose a more radically streamlined queue manager,
> where the trivial-rewrite lookups are performed as a last step in
> "cleanup", leaving the queue manager to just schedule delivery agents,
> without any need to perform external lookups of any sort.
>
> If per-user content filtering amounted to consulting an alternate
> transport table in trivial-rewrite (based on a flag in the queue manager
> resolve request), I have no objections as the mechanism would have the
> same queue manager latency as the current Postfix. This could again be
> implemented in cleanup as above, with cleanup requesting either the
> regular or the filter transport table.

Forgive me for perpetuating this thread but I'm not sure that will provide the
functionality I would like to see. I would like to see some of the functionality
of smtpd's check_xxx_access replicated for filtering, namely:

        check_client_filter (works like check_client_access)
        check_sender_filter (works like check_sender_access)
        check_recipient_filter (works like check_recipient_access)

Within these checks the RHS values would be:

        OK -> do not filter (ie leave transport:next_hop alone)
        transport:next_hop -> use this transport:next_hop instead

I also would like to see

        filter_classes (works like smtpd_restriction_classes)

to provide exceptions.

Why am I harpiong on this? I feel I have what seems to be a fairly complex
set of requirments and conditions to live with:

a) the filter host is not local
b) customers have a requirement that some mail must *not* be filtered
c) we sell
        filter outgoing and incoming
        filter outgoing only
        filter incoming only
        allow exceptions

I have implemented a pure postfix setup (two instances of postfix; could
have done it with one but yet more requirements make using 2 easier) that
does all of this when there's only one recipient per email. If there are
multiple recipients (in different domains) then I can't guarantee both of
these:

- mail that should be filtered, is
- mail that should not be filtered, isn't

Maybe my setup is too simple and I need to add one or more postfix instances
although I could implement the filtering checks I need in a local filter based
on smtpprox. Will give this some thought over this long weekend.

This should be the last you hear from me on this unless you want more :-)

Colin
--
Colin Campbell
Unix Support/Postmaster/Hostmaster
CITEC
+61 7 3227 6334

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