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List:       james-user
Subject:    Re: Anti-spam
From:       Eric Charles <eric () apache ! org>
Date:       2013-10-26 7:35:26
Message-ID: 526B70BE.7040506 () apache ! org
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Basic documentation regarding antispam here:

http://james.apache.org/server/3/config-antispam.html

On 15/10/13 23:20, David Legg wrote:
> Hi Pete,
> 
> I've had James 2.3.1 running since forever on a small internet facing
> server.
> 
> I installed the Bayesian filter back when even one spam during the day
> was an event in itself!  Now it protects us from hundreds a day!  In
> fact looking at the logs it rejected 704 so far today.  So I just wanted
> to say that it works very well.
> 
> The Bayesian filter as supplied in James is very old and the theory
> behind them has improved a lot.  The one in James doesn't attempt to
> decode the email.  This means it analyzes base64 encoded messages
> without decoding the base64 text.  Likewise it makes no attempt to
> ignore images or attachments and therefore it fills its corpus with a
> lot of random looking junk.  However despite this it still manages to
> detect spam reasonably well provided you keep it trained and that means
> sending it ham as well as spam.
> 
> With hindsight I  shouldn't have set it up to delete emails that are
> thought likely to be spam.  It keeps the database small sure... but it
> is a pain to restore an email that was wrongly deleted.  In fact to
> restore a deleted email I have to go into MySQL's binary logs, search
> for that part of the log that inserted the email into the spool and then
> save it into a stand-alone file that can be read by an email reader.
> That's not something I like to do too often.
> 
> In a future setup I think I'll move over to James' IMAP server and
> simply move suspected emails into a 'bad' list that the user can trawl
> through when they think something has been mis-classified.
> 
> At present I've been experimenting with N-gram based bayesian filters as
> I think they hold a lot of promise.  If I get something up and running
> I'll contribute it to James... but time is precious at the moment so it
> won't be soon.
> 
> The Bayesian implementation used in the Thunderbird client is excellent
> [1] and the JunQuilla Thunderbird extension [2] by rkent is really good
> for managing the corpus and showing which keywords contributed to the
> 'spaminess' of the email.  I know this doesn't really answer your
> question of what off-the-shelf software to use but I hope it reduces
> your suspicion about Bayesian filters.
> 
> I've looked at lots ideas for rejecting spam; everything from
> greylisting [3], tarpitting [4], DNSBL, URIBL, VERP [5], SPF [6],
> Teergrubing [7] etc etc.
> 
> However, they all have weaknesses and in the end I firmly believe that
> Bayesian analysis is the best way forward as it is the only method I've
> seen which adapts as the spam adapts.
> 
> Regards,
> David Legg
> 
> 
> [1]
> http://mozilla.inkedblade.net/source/mozilla/mailnews/extensions/bayesian-spam-filter/src/
>  [2] http://mesquilla.com/extensions/junquilla/
> [3] http://projects.puremagic.com/greylisting/whitepaper.html
> [4] http://www.spamcannibal.org/cannibal.cgi
> [5] http://cr.yp.to/proto/verp.txt
> [6] http://www.openspf.org/
> [7]
> http://altlasten.lutz.donnerhacke.de/mitarb/lutz/usenet/teergrube.en.html
> 
> On 15/10/13 12:54, Pete Williams wrote:
> > Hi
> > 
> > I'm trying to find out what I need to do to implement an effective anti-spam \
> > solution. 
> > We currently use James 2.3.2 but are working on an upgrade.
> > 
> > I have found the Bayesian mailets, but would like to know if there is anything \
> > else as a don't set a great deal of store by these methods. I'd rather just try \
> > reverse mx look-ups, banning known black holes as a start. 
> > Any help appreciated.
> > 
> > Cheers,
> > 		 	   		
> 
> 
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