[Mailman-Users] mail loops: list-request and vacation messages

Chuq Von Rospach chuqui at plaidworks.com
Tue Jun 26 06:36:22 CEST 2001

On Monday, June 25, 2001, at 09:19 PM, Barry A. Warsaw wrote:

> Nope, and I agree with everything you've said.  What I was thinking of
> was flagging situations where you see 10 or 50 or 100 posts from the
> same address in the span of a couple of minutes.

But you won't see that, Barry. Think about how a loop operates. You send 
a message to someone with a dweeby mailbot. it responds. that response 
goes back into your incoming queue, and gets sent out again. Then the 
mailbot responds again. For the mailbot to respond that frequently, it 
not only has to be on a very lightly loaded system with quick turnaround 
and a fast pipe, but your mailman system has to be able to churn out 
that quickly, too.

I think the absolute worst I've ever seen on a mailbot loop was about 
1200 in an hour -- and that didn't involve a MLM, just to dueling 
mailbots (mine was stupid and fast, too. I fixed it). Instead, what 
you're likely to see is the message returning once per qrunner instance, 
more or less. It's not a flood, it's a long, slow trickle leading to 

I think you can do pretty much everything you want to do without 
actually rate limiting, and get side benefits as well.

If you:

continue to track X-beenthere

>     CVR> If 2.1 doesn't do it, keeping track of message-id's and
>     CVR> locking down repeated ones is a good idea.

bounce duplicate message-ids.

>     CVR> So is building a suite of keywords "out of the office", "on
>     CVR> vacation" that lock to admin approval.

do the suite of keywords

and do two other things:

trap any message with a default digest subject line, and

trap any message with the list footer included in the reply

you'll trap pretty much every damn loop out there early and often. The 
two content traps are significant -- because chances are, the loopbot 
will simply return a "Re: today's dweeby digest V1#13 (I am on 
vacation), so if you trap on dweeby digest, you trap the bot. Or they 
include your message in their response, which includeds the standard 
footer, which includes text you can trap against, if you word it right.

Some folks, however, would consider those false positives, since they 
will also trap 'real' replies. My research (and I've actually done a 
number of user surveys on this....) actually indicate you're enforcing 
netiquette instead, and the users you honk off by doing so are far 
outnumbered by the ones who are sick and tired of people who don't edit 
included messages or fix the @#$@#$#@ subject line when replying to 
digests. So you get some free benefit and solve two problems at once...

I did a LOT of this kind of filtering on my heavily-hacked majordomo 
system. I got a complaint a montha bout being a content nazi, and they 
were usually about that friendly. (on the other hand, before I started 
bonking "dweeby digest #...." subject lines, I got about a dozen 
complaints a month to do something about it, and there was usually a 
fight going on on ONE of the lists where users were arguing about it.). 
Since I moved to mailman, I dropped all that, to see what happened. 
Short answer; users quickly fell back into old, lazy habits, and other 
users quickly started writing me asking me to PUT IT BACK. Even many who 
bitched at me for doing it in the first place. Once they saw what it was 
trapping -- they understood...

I just haven't had time...

when I had my hacks in place, I had very, very few loops sneak through. 
they had to work hard to do it. Mailman's actually pretty good about it, 
and I'd say 95% of the loops that do sneak through could be tgrapped by 
trapping the default digest subject line, but that's mostly because 
digests coerce reply-to (they basically have to. I can't justify 
reply-to-nobody, but it's tempting), and that's what usually starts 
loops in the first place....

Chuq Von Rospach, Internet Gnome <http://www.chuqui.com>
[<chuqui at plaidworks.com> = <me at chuqui.com> = <chuq at apple.com>]
Yes, yes, I've finally finished my home page. Lucky you.

Always look away from the obvious answers, because if you don't find
a better one, you can always go back to them on short notice.

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