elmo prodded me on IRC that my mail host was refusing spam with a “550 Message classified as spam”. While this is correct, it causes double-bounces to go to postmaster@debian.org, which is unintentional. At Samfundet we have a setup which doesn’t bounce spam sent to lists, it just accepts it and nullroutes it. I don’t think that’s the right way, but it’s better than annoying postmaster@debian with bounces.

I’m using exim4, and this is how I solved it. I replaced my normal spam-bounce rule:

     deny message = This message was classified as SPAM
       spam = nobody:true
       condition = ${if >={$spam_score_int}{100}}{1}{0}}

with:

     deny message = This message was classified as SPAM
       spam = nobody:true
       condition = ${if and {\
                 {!match{$recipients}{tfheen@err.no}}\
                 {!match{$sender_address}{tfheen@debian.org}}\
                 {>={$spam_score_int}{100}}\
                 }{1}{0}}

     warn message = X-err-Devnull: spam
             log_message = Eaten by spam filter \
                         (score=$spam_score, req=10.0)
             spam = nobody

In addition, a special router is needed; mine is called 50_err_devnull:

# A special driver that redirect "X-err-Devnull"-ed mail (spam and
# virus sent to mailing lists, see the DATA ACLs) to /dev/null

err_devnull:
        driver = accept
        condition = ${if def:h_X-err-Devnull: {1}{0}}
        transport = devnull

Finally, the devnull transport:

# Archive the mail in /dev/null
devnull:
  debug_print = "T: devnull for $local_part@$domain"
  driver = appendfile
  file = /dev/null

This is a bit hard-coded and could probably be fixed a bit better, but it seems to work fine for me, at least.

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