> On Aug 16, 2017, at 1:53 AM, Rick van Rein <r...@openfortress.nl> wrote:
>
> I was focussing on passing feedback for individual recipients in a
> one-by-one fashion from lmtpd back to lmtp, but it is actually even
> nicer to do it per group -- so that a resend can be tried for the
> group and they get to see each other's addresses to share.
The above does not make much sense to me. Whatever the batching
of recipients into SMTP envelopes (possibly down to "singleton"
messages per recipient) each such message may as well be re-injected
via SMTP, and its response "stuttered" per envelope recipient back
to the upstream LMTP client. You will of course need to be careful
to maintain the proper order of "." responses to match the order of
"2XX" "RCPT TO" responses in the upstream envelope.
You content filter should open multiple SMTP sessions in parallel
and clone as much of the message body as possible to each one
round-robin. The collect all the "." responses in parallel,
associate each one with the right list of upstream recipients,
then transmit all the per-recipient replies upstream in the
right order.
Since the re-injection Postfix service just writes a queue
file and does not split envelopes (that happens later when
the queue manager passes recipient batches to delivery
agents) there's no option of that service giving usefully
different per-recipient replies at ".".
So, while an "lmtpd" in Postfix would not be difficult
to implement, it would not be useful.
--
Viktor.
