configs/config.samples/F001

   1 From: Ephraim Silverberg <ephraim@cs.huji.ac.il>
   2 Date: Tue, 17 Feb 1998 12:55:55 +0200
   3
   4 We're using Exim 1.82 and have written a message filter to intercept spam
   5 messages that RBL doesn't catch.  Since we have met with reasonable success
   6 since installing (and refining) the filter -- 566 genuine spam messages
   7 intercepted during a time period where there were 67 RBL rejections -- I
   8 thought that the rest of the list may be interested in reviewing our filter
   9 as a starting point for their own system message filter.
  10
  11 There are a number of caveats, however:
  12
  13 1. The suspected spam is not automatically rejected as RBL hosts are, but
  14    is saved to a folder that should be read/writable by the mail
  15    administrators.  The reason for this is that the filter catches also
  16    some legitimate mail and these messages should be bounced to their
  17    originally intended recipient(s) (ala X-Envelope-To:) and the filter
  18    refined and/or the databases (described below) updated.
  19
  20 2. My filter traps blank/non-existent To: lines as well as To: lines
  21    contained in From: lines, but firsts exempts the following categories
  22    from this check: mailing lists, local mail, mail originating in the
  23    country (e.g. in our case *.il) and mail coming from autosupport servers.
  24
  25 Beyond implicit checks, it uses four DBM databases: two that exempt the
  26 message from any spam (beyond RBL) checks (software servers and strange mailing
  27 lists need to be here) -- one based on $sender_address and the other on
  28 $header_to: lines -- and, conversely, two databases for known spammers that
  29 have valid mail headers that aren't caught by implicit checks. All entries
  30 in these databases are lowercase so that we don't need two lines for
  31 'friend@public.com' and 'Friend@Public.com'.
  32
  33 The sample filter package is at ftp://ftp.cs.huji.ac.il/pub/exim/spam_filter/
  34
  35 Comments and suggestions are welcome.