[Mailman-Users] rejecting messages *to* non-members

glen martin glenm at locutory.org
Thu Nov 26 22:52:39 CET 2009

Yah ... and responding to another note in the thread, it wouldn't stop
them from using bcc.  But I judge these errors to be lazy, not
malicious.  These users can easily send a note direct to other folks,
even forwarding the email they sent to the list if that is what they
really want to do.  But it is easier for them to just add their other
recipient to the one email, so that is what they do. Until this means
their email doesn't get to the list at all, at which point the 'easy'
solution is a different one. Or so I hope.

Again responding to another suggestion in this thread, the use of
recipient counts is an option I hadn't thought of.  The potential
problem here is I don't set a reply-to header, by and large their
clients don't have reply-list, so they use reply-all to respond to the
list. if we get a few messages deep into a thread, reply-all will go to
the list plus a couple of earlier senders, which will confuse the
recipient count.  Hmmm, maybe this would work if duplicate addressees
are removed earlier than the count filter.

The smtp solution was one I really hadn't considered, and while I'm sure
it could work, it seems very brute force. It seems to me that this is
something that should be configured for the list, not in postfix where
it gets involved in all mail handling.

I'm thinking about a custom handler ... it doesn't look like a hard
problem, just loop through the recipient list (recips), and look up
whether each of them is a list member. Reject on failure, fall through
and pass.  The hardest part will be figuring out now python works ...

Thanks to everyone for the responses and suggestions so far, much

Geoff Shang wrote:
> On Wed, 25 Nov 2009, glen martin wrote:
>> I've got some rude users who occasionally cc non-list members on 
>> their messages to a restricted list that is actually intended to be 
>> private (membership by invitation only).  Then, as you might expect, 
>> when the non-member replies, that message is rejected or held for 
>> approval.  This doesn't seem friendly.
>> The root cause, though, is my users.  I'd therefore like to train 
>> them :) by rejecting their posts that copy non-members.
> Just to make the point that rejecting such posts obviously wouldn't 
> prevent them from reaching the off-list recipients that are being 
> copied. But I assume you know this.
> Geoff.
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