Questions regarding headers that may occur multiple times

[mbw+nm@mailbox.org]

Hi there,

I have been using notmuch in conjunction with neomutt and some homemade
tagging scripts more or less successfully for about two years now.

However, sometimes I have difficulties to uniquely identify (and thus tag
accordingly) the intended recipient of an email. For that I wanted to
try to use the `Delivered-To` and `Received:` headers.

These may occur an arbitrary amount of times within a given email. But
from what I gather by first reindexing with

`$ notmuch config set index.header.Received Received`

`$ notmuch reindex '*'`

and then inspecting the result via

`$ notmuch config set show.extra_headers="received;delivered-to"

`$ notmuch show --format=json date:today | jq`,

it appears that only the first occurrence of these header values are
taken into account?

I might be wrong, so I'll just try to describe what problem I am trying
to solve:

Consider an email that looks like this:

Return-Path:
        <0101017ee5317599-02f47ee2-4eda-4840-abbd-7d52b54ff13b-000000@us-west-2.amazonses.com>
Delivered-To: unknown
Received: from pop3.mailbox.org ([2001:67c:2050:106::143:199]:995) by
        legion.localdomain with POP3-SSL getmail6 msgid:UID12422-1430074968; 10 Feb
        2022 20:27:40 -0000
Delivered-To: mbw+nm@mailbox.org
Received: from director-05.heinlein-hosting.de ([80.241.60.215])
        (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits))
        by dobby23a.heinlein-hosting.de with LMTPS
        id 2GLdD/RsBWLLYwEAwSxZKQ
        (envelope-from
        <0101017ee5317599-02f47ee2-4eda-4840-abbd-7d52b54ff13b-000000@us-west-2.amazonses.com>)
        for <mbw+nm@mailbox.org>; Thu, 10 Feb 2022 20:52:20 +0100
Received: from mx2.mailbox.org ([80.241.60.215])
        (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits))
        by director-05.heinlein-hosting.de with LMTPS
        id +M7kDfRsBWJYZAEATazItQ
        (envelope-from
        <0101017ee5317599-02f47ee2-4eda-4840-abbd-7d52b54ff13b-000000@us-west-2.amazonses.com>)
        for <mbw+nm@mailbox.org>; Thu, 10 Feb 2022 20:52:20 +0100
X-Virus-Scanned: amavisd-new at heinlein-support.de
etc.

Here, the information visible with `notmuch show` includes `Received:
from pop3.mailbox.org` (good) and `Delivered-To: unknown` (bad).

What I would like to do is to somehow access the second (or maybe all)
occurrences of these header values. Is that possible?

This would allow me to identify emails which `To: all@some-mailing-list.net`.

It also appears that (with notmuch 0.35), the `extra_headers` only show
up with `--format.json`, by the way.

I'd be grateful for any suggestions on how to approach this.


Cheers,
Max