From: Victor Duchovni (Victor.DuchovniMorganStanley.com)
Date: Mon Aug 01 2005 - 11:56:34 CDT

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On Mon, Aug 01, 2005 at 12:18:09PM -0400, Scott Merrill wrote:

> This works fine for people not directly addressed by CLIENT in the
> original messages; but people included on the To or Cc lines are getting
> duplicate messages, causing some confusion.

Solve the duplicate delivery problem. The "always_bcc" approach is
correct. Sometimes the best approach here is expectation management.

> I _think_ I want to use an after-queue content filter to modify the
> incoming messages from CLIENT. I hacked Bennett Todd's smtpprox filter
> to determine which local recipients were not already recieiving the
> message, and then add a BCC header for them.

No, most MTAs discard "Bcc" headers, and disclosing Bcc is a bad idea.

> I'm using virtual users, so I can't rely on procmail.

You can likely use "procmail" and/or "formail" with Courier "maildrop".

> Management really wants the _original_ message sent to all necessary
> local recipients, so that they can see who else was included in the
> original delivery. Otherwise I'd just use a script to forward copies to
> the necessary recipients.

Be clear on who needs to see the full recipient list:

    - Just the always_bcc recipients (who may in some cases
    also be listed in To: or Cc:)?

    - All envelope recipients, regardless of whether they are
    on the always_bcc list or were header recipients or not?

A good way to manage always_bcc supervisory copies is to encapsulate
the original message as a message/rfc822 attachment to the supervisory
copy, with the full envelope listed in the body of the supervisory mail:

    From: SuperVisory Mail <supervisoryexample.com>
    To: acme-supervisors <acme-supervisorsexample.com>
    Subject: Message from joeacme.com
    Content-Type: multipart/mixed;
            boundary = "supervise-me-<32_random_hex_digits>"

    --supervise-me-<32_random_hex_digits>
    Content-Type: text/plain; charset = us-ascii

    To: <env-recipient1>
    To: <env-recipient2>
    ...
    To: <env-recipientN>

    --supervise-me-<32_random_hex_digits>
    Content-Type: message/rfc822

    Received: ...
    From: joeacme.com
    To: ... some alleged recipients ...
    Cc: ... some more alleged recipients ...
    Subject: ...

    content

    --supervise-me-<32_random_hex_digits>--

Because your supervisory encapsulation is for a sender address (rather
than archival of all recipient addresses), it is difficult to capture
the message envelope recipients, since the bcc and the recipients
are potentially sent in different delivery transaction (split envelope).

The only viable approach is indeed a content filter that intercepts all
deliveries, and generates a Bcc encapsulated copy. Consider using a high
mumble_destination_recipient_limit (if "mumble" is the filter transport)
to force as many recipients as possible into a single delivery (and
raise the post-filter smtpd_recipient_limit if to match if necessary).

--
        Viktor.

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