On Thu, Apr 24, 2025 at 09:43:34AM -0400, Wietse Venema via Postfix-users wrote:
> > This is a sketch, fill in the details and test with care.
>
> I wish this were easier. If Postfix were to provide native support,
> what should it look like? I'm thinking of an intermediate program
> that annotates a message and that ultimately relies on existing
> Postfix mechanisms for final delivery (translation: it would not
> be my first choice to combine annotation with final delivery).
>
> What would the annotation look like? Prepend more message headers,
> or generate a completely new message with the original message
> attached as message/rfc822?
My sense is that encapsulation as a multipart with the original message
attached, and a machine-readable metadata MIME part that details the
envelope, ... is the way to go. There may already be documented
formats along these lines understood by some email archive products.
> How/where are delivery errors reported?
Definitely not the original sender. Some sort of postmaster address,
possibly with the data stored locally out of the queue, waiting for
manual intervention to move it into the archive. In other words,
perhaps guaranteed to never bounce be at the cost of potentially
runnig the system out of disk space if neglected indefinitely.
> When would the annotation happen? At the time that the message is
> received (i.e. with mostly original envelope info) or at te time it
> is delivered to an eligible recipient (the envelope contains the
> final envelope info)?
That should be up to the administrator, there are potential advantages
in having this happen closer to delivery, as the recipient data may
be more fine-grained. But often just south of virtual alias expansion
can be implemented with a two-stage Postfix multi-instance design with
alias expansion in the input queue, and archiving in the output queue.
> Last but not least, what are the relevant industry
> standards/conventions?
It's a been a ~1.5 decades since I've been actively involved this, so
perhaps some other readers can give a better answer.
--
Viktor.
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