My recollection of the debate about l= is that there were about as
many theories about the point of l= as there were people promoting it.
The main theory I remember was about hypothetical mailing lists that
were too incompetent to filter incoming spam so the list recipients
would do it based on the signatures of messages that passed through
the list.
Except we now know that one major piece of list software can preserve the
signature, depending on whether subject is signed / preserved.
I don't think anyone denies that there are some cases when a signature
will survive some mailing lists, although the list software I've seen is
all moving in the other direction -- mj2 will remove and flatten MIME
parts and Yahoo groups rewrites HTML to add footers, for example.
The question that I've never seen addressed is why bother? Why would you
want to filter list mail based on the contributor's signature rather than
the list's signature? If a list were having trouble with spam leaking
through, would you expect the list manager to adjust the config to leak
more perfectly, or fix the leak? Over the past two decades mailing lists
have developed use all sorts of techniques to manage what gets onto the
list and to keep out unwanted mail, and I've never seen a plausible
explanation of why anyone would expect that to reverse so completely that
list recipients would need to do per-message spam filtering.
R's,
John
PS: We do bozo filtering of list mail, but that's easy -- you already know
if the mail is from the list, so if the From: header says you know who,
you ditch it. That's two lines of procmail.
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