List Spam Filtering

Da Rock freebsd-questions at
Wed May 15 02:23:50 UTC 2013

On 05/12/13 22:04, Rich Kulawiec wrote:
> 1. Restricting mailing lists to "subscribers only" has been a best
> practice since the last century.  It's a very good anti-spam tactic.
> 2. However, doing so -- for a list run via Mailman, like this one --
> does not pose a significant impediment for non-subscribers.  By default,
> Mailman will hold traffic from non-subscribers for list-owner approval.
> Provided the list-owners check that queue periodically and have reasonable
> spam-spotting abilities, this works beautifully.
> 3. Note that Mailman, as part of that same mechanism, allows list-owners
> to add non-subscribers to a list of those permitted to send traffic to
> the list without approval.  This feature is probably more often used to
> allow traffic from alternative addresses for subscribers, e.g., someone
> is subscribed as fred at but sends occasionally from fred at
> But it can just as easily be used for non-subscribers if the list-owners
> so choose.
> 4. List-owners may also find it useful to keep track of which spammers
> repeatedly attempt to abuse the list and block them at the MTA -- which
> has the desirable side effect of blocking them from ALL lists.  I do this
> on a user/host/domain/network basis, and it's proven itself to be worth
> the effort.
> So: setting the "subscribers-only" flag on Mailman has major advantages,
> at the cost of additional work on the part of list-owners -- which can
> be mitigated in part across all lists by making changes to the MTA.
I'm a big fan of _not_ having to subscribe to a list to get a quick hand 
with a one off problem (obviously not this one!)- otherwise too many 
lists get subscribed to, oodles of messages come in which you can't do 
anything about and so forth (so its not simply just a matter of 
subscribe, unsubscribe as noted). Unfortunately, many see it as a spam 
filter and thereby abuse it. How often do you need help with an issue 
with libreoffice, mozilla whatever, or other application? And yet 
subscription is compulsory and a ton of messages (devs convs mostly) 
come flooding in within minutes.

Aside from all that, the last suggestion (4) should be possible using 
some simple filtering without the need to change the subscription 
parameters. It could be possible to even do it automatically saving 
further work on a list-owner.

I admit the spam is getting worse, but there are still many more users 
sending who would like try before they buy - or subscribe. FreeBSD is an 
OS, yes, but it does give users options and freedom; and although many 
are willing to give up their freedom because it is *appears* safer, they 
tend to have serious regrets in the light of day. Better to find a way 
to maintain the freedom (and minimise the overheads required for 
oversight) through other measures.

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