> On Apr 14, 2024, at 3:33 PM, Andrew Reilly <arei...@bigpond.net.au> wrote:
>
>
> Over the weekend I got around to investigating, and discovered that the
> errant messages don’t _have_ a Sender: header. There’s a Return-Path: header
> that captures the envelope-from, but I haven’t figured out how to make sieve
> check that yet: it doesn’t seem to like it. Sieve documentation is
> spectacularly inconclusive, but I suspect that the envelope extension might
> do what I want, but that’s not really my question.
>
> Does anyone know why the Sender: header, which used to be so reliable that I
> had thought it an intrinsic part of the SMTP/MTA ecosystem, has gone away, or
> is at least not ubiquitous?
The Sender: field is optional. I don't know why FreeBSD stopped using it but I
filter on List-Id: (which is used by pretty much every mailing list), which
seems more appropriate.
