Me "spamming" this list...

Arno Wagner wagner at
Fri May 31 13:52:01 CEST 2002

Dear gnupg-devel list members,

in the last 48 hours (or so) this list has received messages
from my spam-detector about spam being dropped. 

I am sorry about this, please accept my apology!

I think I should explain what happened, so maybe others can 
avoid the mistakes I made: I have a very manual spam filter,
that I maintain by just adding to my .procmailrc. For hard spammers
I just drop the mail, for others I had an auto-reply feature. 
While I was careful all my receipes are restrictive enough not
to be overly trigger-happy, I did not take into account the
possibility for a different kind of error. 

What I effectively did in one match-expression whas replace the
leading "*" with a "$". As a result this rule appearently matched for
every Email that came in. As a consequence every email to me got a
notification about it being spam and dropped, which also happened to
all the messages telling me there was something wrong on my side.

To make things worse, we had an announced partial network outage 
on Wednsday (routing tables cleanup) so I was not suspicous about
not getting any email. I was not at work on Wednsday, so I 
finally found out about the problem when somebody phoned me
Thursday morning. 

At that time I had about 30 messages telling me about the problem
and about 400 Messages from a mail-loop, that happened despite 
my measures to prevent loops.

Lessons learned on my side:

  - Don't send out automatic responses to, if the trigger-
    mechanism has a single point-of-failure!

    For the time being I make that: Don't send out any automated

  - Doing full logging is a very good idea when automatically 
    deleting messages!  

    Because I at least got this right, I did not loose any 
    messages and was able to identify everybody that I needed to
    apologize to.

  - If you screw up, apologize a.s.a.p. to those affected and
    explain what happened!     

  - Look at statistics frequently! 

    My previous set-up gave me one spam-summary per week. That is 
    not enough, now I am getting a daily summary.  

  - Make sure you understand the problem! 

    My mail-loop detection scheme used a field in the header with 
    a magic number. That is fine for every loop that keeps the 
    auto-response somewhere in the replys, but this one list-admin 
    daemon just send me a completely fresh email about not 
    understanding my command. Practical loop detection is obviously
    more complicated than I thought ....

Once again, please accept my apologies for this incident!


Arno Wagner, Communication Systems Group, ETH Zuerich, wagner at
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
For every complex problem there is an answer that is clear, simple, 
and wrong. -- H L Mencken

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