[Mailman-Users] Detecting mail with multiple From: lines

[Jay A. Sekora]

On Mon, 2011-05-23 at 18:01 +0200, Lucio Chiappetti wrote:
> > Mail sent on behalf of a group, such as mail from a committee or from 
> > the multiple authors of a paper, where you want people's individual 
> > addresses and names exposed
> 
> But surely that does not require multiple From lines, like a message 
> addressed to many persons does not have multiple To lines, but a To (or 
> From) line consisting of a list of addresses.

No, certainly not.  (Although I have seen a fair bit of the latter --
multiple recipients each listed in their own To: header -- in legitimate
mail.  My vague recollection is that most such mail I've seen was
gatewayed from tools which are primarily designed for intranets or other
non-Internet networks.)  However, the problem of sender filters only
being applied to one of the multiple possible sender addresses would
still apply in this case, so one way or another, if you want to be able
to blacklist at the Mailman level individual (claimed) sender addresses
when a message has multiple From: addresses (whether listed in one
header or each listed in their own header), it sounds like you need to
do it with a spam filter of the sort Mark suggested, rather than with
the more intuitive sender filters.

[digression more appropriate for an actual spam-filtering list snipped.]

> I've used myself a From (and/or a Reply-To) line listing more than one
> addresses (inserting them at MUA level in the ONLY From line allowed
> by the MUA), when I wanted replies forced to more than one address.

As an aside, I'd trust MUAs to do the right thing with multiple
addresses in a Reply-To: line more than I'd trust them to do the right
thing with multiple addresses in a From: line, just because the latter
is so rare.  (Suspenders *and* a belt should be fine, though. :-)

Jay